Multi-layer golf ball

ABSTRACT

Disclosed herein is a multi-layer golf ball having a soft outer cover. The golf ball has an inner cover layer with a Shore D hardness of 60 or more, and an outer cover with a Shore D hardness of 55 or less, and more preferably 50 or less. In a particularly preferred form of the invention, the outer cover comprises one or more polyurethane materials. The golf ball of the invention has exceptionally soft feel and high spin rates on short shots of 80 yards or less and, particularly, 40 yards or less, while maintaining good distance and average spin on full shots.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 09/783,484 filed on Feb. 14, 2001, which is acontinuation-in-part of U.S. application Ser. No. 09/040,456 filed onMar. 18, 1998, now U.S. Pat. No. 6,213,894, which is acontinuation-in-part of U.S. application Ser. No. 08/631,613 filed onApr. 10, 1996, now U.S. Pat. No. 5,803,831, which is acontinuation-in-part of U.S. application Ser. No. 08/591,046 filed onJan. 25, 1996, now abandoned, and a continuation-in-part of applicationSer. No. 08/542,793 filed on Oct. 13, 1995, now abandoned, which in turnis a continuation-in-part of U.S. application Ser. No. 08/070,510 filedJun. 1, 1993, now abandoned. This application is also acontinuation-in-part of U.S. application Ser. No. 09/411,690 filed onOct. 1, 1999, which is a continuation-in-part of U.S. application Ser.No. 09/040,798 filed on Mar. 18, 1998.

FIELD OF THE INVENTION

[0002] The present invention relates to golf balls and, moreparticularly, to improved golf balls comprising multi-layer covers whichhave a hard inner layer and a relatively soft outer layer.

BACKGROUND OF THE INVENTION

[0003] Traditional golf ball covers have been comprised of balata orblends of balata with elastomeric or plastic materials. The traditionalbalata covers are relatively soft and flexible. Upon impact, the softbalata covers compress against the surface of the club producing highspin. Consequently, the soft and flexible balata covers provide anexperienced golfer with the ability to apply a spin to control the ballin flight in order to produce a draw or a fade, or a backspin whichcauses the ball to “bite” or stop abruptly on contact with the green.Moreover, the soft balata covers produce a soft “feel” to the lowhandicap player. Such playability properties (workability, feel, etc.)are particularly important in short iron play with low swing speeds andare exploited significantly by relatively skilled players.

[0004] Despite all the benefits of balata, balata covered golf balls areeasily cut and/or damaged if mis-hit. Golf balls produced with balata orbalata-containing cover compositions therefore have a relatively shortlife-span.

[0005] As a result of this negative property, balata and its syntheticsubstitutes, trans-polybutadiene and transpolyisoprene, have beenessentially replaced as the cover materials of choice by new covermaterials comprising ionomeric resins.

[0006] Ionomeric resins are polymers containing interchain ionicbonding. As a result of their toughness, durability and flightcharacteristics, various ionomeric resins sold by E.I. DuPont de Nemours& Company under the trademark “Surlyn®” and more recently, by the ExxonCorporation (see U.S. Pat. No. 4,911,451) under the trademarks “Escor®”and the designation lotek®, have become the materials of choice for theconstruction of golf ball covers over the traditional “balata”(transpolyisoprene, natural or synthetic) rubbers. As stated, the softerbalata covers, although exhibiting enhanced playability properties, lackthe durability (cut and abrasion resistance, fatigue endurance, etc.)properties required for repetitive play.

[0007] Ionomeric resins are generally ionic copolymers of an olefin,such as ethylene, and a metal salt of an unsaturated carboxylic acid,such as acrylic acid, methacrylic acid, or maleic acid. Metal ions, suchas sodium or zinc, are used to neutralize some portion of the acidicgroup in the copolymer resulting in a thermoplastic elastomer exhibitingenhanced properties, i.e. durability, etc., for golf ball coverconstruction over balata. However, some of the advantages gained inincreased durability have been offset to some degree by the decreasesproduced in playability. This is because although the ionomeric resinsare very durable, they tend to be very hard when utilized for golf ballcover construction, and thus lack the degree of softness required toimpart the spin necessary to control the ball in flight. Since theionomeric resins are harder than balata, the ionomeric resin covers donot compress as much against the face of the club upon impact, therebyproducing less spin. In addition, the harder and more durable ionomericresins lack the “feel” characteristic associated with the softer balatarelated covers.

[0008] As a result, while there are currently more than fifty (50)commercial grades of ionomers available both from DuPont and Exxon, witha wide range of properties which vary according to the type and amountof metal cations, molecular weight, composition of the base resin (i.e.,relative content of ethylene and methacrylic and/or acrylic acid groups)and additive ingredients such as reinforcement agents, etc., a greatdeal of research continues in order to develop a golf ball covercomposition exhibiting not only the improved impact resistance andcarrying distance properties produced by the “hard” ionomeric resins,but also the playability (i.e., “spin”, “feel”, etc.) characteristicspreviously associated with the “soft” balata covers, properties whichare still desired by the more skilled golfer.

[0009] Consequently, a number of two-piece (a solid resilient center orcore with a molded cover) and three-piece (a liquid or solid center,elastomeric winding about the center, and a molded cover) golf ballshave been produced to address these needs. The different types ofmaterials utilized to formulate the cores, covers, etc. of these ballsdramatically alters the balls' overall characteristics. In addition,multi-layered covers containing one or more ionomer resins have alsobeen formulated in an attempt to produce a golf ball having the overalldistance, playability and durability characteristics desired.

[0010] This was addressed by Spalding Sports Worldwide, Inc., theassignee of the present invention, in U.S. Pat. No. 4,431,193 where amulti-layered golf ball is produced by initially molding a first coverlayer on a spherical core and then adding a second layer. The firstlayer is comprised of a hard, high flexural modulus resinous materialsuch as type 1605 Surlyn® (now designated Surlyn® 8940). Type 1605Surlyn® (Surlyn® 8940) is a sodium ion based low acid (less than orequal to 15 weight percent methacrylic acid) ionomer resin having aflexural modulus of about 51,000 psi. An outer layer of a comparativelysoft, low flexural modulus resinous material such as type 1855 Surlyn®(now designated Surlyn® 9020) is molded over the inner cover layer. Type1855 Surlyn® (Surlyn® 9020) is a zinc ion based low acid (10 weightpercent methacrylic acid) ionomer resin having a flexural modulus ofabout 14,000 psi.

[0011] The '193 patent teaches that the hard, high flexural modulusresin which comprises the first layer provides for a gain in coefficientof restitution over the coefficient of restitution of the core. Theincrease in the coefficient of restitution provides a ball which servesto attain or approach the maximum initial velocity limit of 255 feet persecond as provided by the United States Golf Association (U.S.G.A.)rules. The relatively soft, low flexural modulus outer layer providesfor the advantageous “feel” and playing characteristics of a balatacovered golf ball.

[0012] In various attempts to produce a durable, high spin ionomer golfball, the golfing industry has blended the hard ionomer resins with anumber of softer ionomeric resins. U.S. Pat. Nos. 4,884,814 and5,120,791 are directed to cover compositions containing blends of hardand soft ionomeric resins. The hard copolymers typically are made froman olefin and an unsaturated carboxylic acid. The soft copolymers aregenerally made from an olefin, an unsaturated carboxylic acid, and anacrylate ester. It has been found that golf ball covers formed fromhard-soft ionomer blends tend to become scuffed more readily than coversmade of hard ionomer alone. It would be useful to develop a golf ballhaving a combination of softness and durability which is better than thesoftness-durability combination of a golf ball cover made from ahard-soft ionomer blend.

[0013] Most professional golfers and good amateur golfers desire a golfball that provides distance when hit off a driver, control and stoppingability on full iron shots, and high spin on short “touch and feel”shots. Many conventional two-piece and thread wound performance golfballs have undesirable high spin rates on full shots. The excessive spinon full shots is a sacrifice made in order to achieve more spin which isdesired on the shorter touch shots. It would be beneficial to provide agolf ball which has high spin for touch shots without generatingexcessive spin on full shots.

SUMMARY OF THE INVENTION

[0014] An object of the invention is to provide a golf ball with a softcover which has good scuff resistance.

[0015] Yet another object of the invention is to provide a golf ballhaving a favorable combination of spin rate and durability.

[0016] A further object of the invention is to provide a golf ballhaving a soft cover made from a cover material which is blended withminimal mixing difficulties.

[0017] Another object of the invention is to provide a method of makinga golf ball which has a soft cover with good scuff resistance and cutresistance.

[0018] Another object of the invention is to provide a golf ball whichhas a high spin on shots of 250 feet or less and an average spin on fullshots using a 9 iron.

[0019] Yet another object of the invention is to provide a method ofmaking a durable golf ball with a relatively high spin rate.

[0020] A further object of the invention is to provide a multi-layergolf ball having exceptionally soft feel and high spin rates on shortshots while maintaining good distance on full shots.

[0021] Yet another object of the invention is to provide a multi-layergolf ball having a high spin rate on short shots and not having anexcessive spin rate on long shots.

[0022] Other objects will be in part obvious and in part pointed outmore in detail hereafter.

[0023] In a first aspect, the present invention provides a golf ball,comprising a core, a thermoplastic inner cover layer formed over thecore, the inner cover layer having a Shore D hardness of at least 60 asmeasured on the surface thereof, and an outer cover layer formed overthe inner cover layer, the outer cover layer having a Shore D hardnessof no more than 55 as measured on the surface thereof, the golf ballhaving a PGA compression of 100 or less and a coefficient of restitutionof at least 0.770.

[0024] In another aspect, the present invention provides a golf ballcomprising a core, an inner cover layer formed over the core, and anouter cover layer formed over the inner cover layer. The inner coverlayer has a Shore D hardness of at least 60 as measured on the curvedsurface thereof and is formed of a composition including at least onematerial selected from the group of consisting of polyphenyleneether/ionomer blends, ionomers, polyamides, polyurethanes, polyesterelastomers, polyester amides, metallocene catalyzed polyolefins, andblends thereof. The outer cover layer has a Shore D hardness of no morethan 55 as measured on the curved surface thereof. The golf ball has aspin factor of about 5, a PGA compression of 100 or less, and acoefficient of restitution of at least 0.770.

[0025] In yet another aspect, the present invention provides a golf ballcomprising an inner ball and an outer cover layer formed over the innerball. The inner ball comprises a core and an inner cover layer disposedabout the core. The inner ball has a coefficient of restitution of atleast 0.780. The outer cover layer has a Shore D hardness of no morethan 55 as measured on the curved surface thereof. The golf ball has acoefficient of restitution of at least 0.770 and a PGA compression of100 or less.

[0026] In a further aspect, the present invention provides a golf ballcomprising a core, an inner cover layer disposed about the core, and anouter cover layer disposed about the inner cover layer. The inner coverlayer has a Shore D hardness of at least 60 as measured on the curvedsurface thereof and comprises at least one material selected from thegroup consisting of polyphenylene ethertionomer blends, ionomers,polyamides, polyurethanes, polyester elastomers, polyester amides,metallocene catalyzed polyolefins, and blends thereof. The outer coverlayer has a Shore D hardness of no more than 55 as measured on thecurved surface thereof and comprises at least one material selected fromthe group consisting of polyphenylene etherlionomer blends, ionomers,polyamides, polyurethanes, polyester elastomers, polyester amides,metallocene catalyzed polyolefins, and blends thereof. The golf ball hasa PGA compression of 100 or less and a coefficient of restitution of atleast 0.770.

[0027] The invention accordingly comprises the several steps and therelation of one or more of such steps with respect to each of the othersand the articles possessing the features, properties, and the relationof elements exemplified in the following detailed disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The following is a brief description of the drawings, which arepresented for the purposes of illustrating the invention and not for thepurposes of limiting the same.

[0029]FIG. 1 is a cross-sectional view of a golf ball embodying theinvention illustrating a core 10 and a cover 12 consisting of an innerlayer 14 and an outer layer 16 having dimples 18; and

[0030]FIG. 2 is a diametrical cross-sectional view of a golf ball of theinvention having a core 10 and a cover 12 made of an inner layer 14 andan outer layer 16 having dimples 18.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The present invention relates to improved multi-layer golf balls,particularly a golf ball comprising a multi-layered cover 12 over asolid core 10, and method for making same. The golf balls of theinvention, which can be of a standard or enlarged size, have a uniquecombination of high coefficient of restitution and a high spin rate onshort shots.

[0032] The core 10 of the golf ball can be formed of a solid, a liquid,or any other substance which will result in an inner ball, i.e. core andinner cover layer, having the desired COR, compression and hardness. Themulti-layered cover 12 comprises two layers: a first or inner layer orply 14 and a second or outer layer or ply 16. The inner layer 14 can beionomer, ionomer blends, non-ionomer, non-ionomer blends, or blends ofionomer and non-ionomer. The outer layer 16 is softer than the innerlayer and can be ionomer, ionomer blends, non-ionomer, non-ionomerblends or blends of ionomer and non-ionomer.

[0033] In a first preferred embodiment, the inner layer 14 is comprisedof a high acid (i.e. greater than 16 weight percent acid) ionomer resinor high acid ionomer blend. Preferably, the inner layer is comprised ofa blend of two or more high acid (i.e. at least 16 weight percent acid)ionomer resins neutralized to various extents by different metalcations. The inner cover layer may or may not include a metal stearate(e.g., zinc stearate) or other metal fatty acid salt. The purpose of themetal stearate or other metal fatty acid salt is to lower the cost ofproduction without affecting the overall performance of the finishedgolf ball. In a second embodiment, the inner layer 14 is comprised of alow acid (i.e. 16 weight percent acid or less) ionomer blend.Preferably, the inner layer is comprised of a blend of two or more lowacid (i.e. 16 weight percent acid or less) ionomer resins neutralized tovarious extents by different metal cations. The inner cover layer may ormay not include a metal stearate (e.g., zinc stearate) or other metalfatty acid salt.

[0034] It has been found that a hard inner layer provides for asubstantial increase in resilience (i.e., enhanced distance) over knownmulti-layer covered balls. The softer outer layer provides for desirable“feel” and high spin rate while maintaining respectable resiliency. Thesoft outer layer allows the cover to deform more during impact andincreases the area of contact between the club face and the cover,thereby imparting more spin on the ball. As a result, the soft coverprovides the ball with a balata-like feel and playabilitycharacteristics with improved distance and durability. Consequently, theoverall combination of the inner and outer cover layers results in agolf ball having enhanced resilience (improved travel distance) anddurability (i.e. cut resistance, etc.) characteristics while maintainingand in many instances, improving, the playability properties of theball.

[0035] The combination of a hard inner cover layer with a soft,relatively low modulus ionomer, ionomer blend or other non-ionomericthermoplastic elastomer outer cover layer provides for excellent overallcoefficient of restitution (i.e., excellent resilience) because of theimproved resiliency produced by the inner cover layer. While someimprovement in resiliency is also produced by the outer cover layer, theouter cover layer generally provides for a more desirable feel and highspin, particularly at lower swing speeds with highly lofted clubs suchas half wedge shots.

[0036] Inner Cover Layer

[0037] The inner cover layer is harder than the outer cover layer andgenerally has a thickness in the range of 0.01 to 0.15 inches,preferably 0.01-0.10 inches, more preferably 0.03 to 0.07 inches for a1.68 inch ball and 0.05 to 0.10 inches for a 1.72 inch (or more) ball.The core and inner cover layer together form an inner ball having acoefficient of restitution of 0.780 or more and more preferably 0.790 ormore, and a diameter in the range of 1.48-1.66 inches for a 1.68 inchball and 1.50-1.70 inches for a 1.72 inch (or more) ball. The innercover layer has a Shore D hardness of 60 or more. It is particularlyadvantageous if the golf balls of the invention have an inner layer witha Shore D hardness of 65 or more. The above-described characteristics ofthe inner cover layer provide an inner ball having a PGA compression of100 or less. It is found that when the inner ball has a PGA compressionof 90 or less, excellent playability results.

[0038] The inner layer compositions of the embodiments described hereinmay include the high acid ionomers such as those developed by E.I.DuPont de Nemours & Company under the trademark Surlyn® and by ExxonCorporation under the trademark Escor® or tradename lotek®, or blendsthereof. Examples of compositions which may be used as the inner layerherein are set forth in detail in U.S. Ser. No. 08/174,765, nowabandoned, which is a continuation of U.S. Ser. No. 07/776,803 filedOct. 15, 1991, now abandoned, and Ser. No. 08/493,089, issued as U.S.Pat. No. 5,688,869, which is a continuation of Ser. No. 07/981,751, nowabandoned, which in turn is a continuation of Ser. No. 07/901,660 filedJun. 19, 1992, now abandoned, all of which are incorporated herein byreference. Of course, the inner layer high acid ionomer compositions arenot limited in any way to those compositions set forth in said copendingapplications.

[0039] The high acid ionomers which may be suitable for use informulating the inner layer compositions of the subject invention areionic copolymers which are the metal, i.e., sodium, zinc, magnesium,etc., salts of the reaction product of an olefin having from about 2 to8 carbon atoms and an unsaturated monocarboxylic acid having from about3 to 8 carbon atoms. Preferably, the ionomeric resins are copolymers ofethylene and either acrylic or methacrylic acid. In some circumstances,an additional comonomer such as an acrylate ester (i.e., iso- orn-butylacrylate, etc.) can also be included to produce a softerterpolymer. The carboxylic acid groups of the copolymer are partiallyneutralized (i.e., approximately 10-100%, preferably 30-70%) by themetal ions. Each of the high acid ionomer resins which may be includedin the inner layer cover compositions of the invention contains greaterthan about 16% by weight of a carboxylic acid, preferably from about 17%to about 25% by weight of a carboxylic acid, more preferably from about18.5% to about 21.5% by weight of a carboxylic acid.

[0040] Although the inner layer cover composition preferably includes ahigh acid ionomeric resin and the scope of the patent embraces all knownhigh acid ionomeric resins falling within the parameters set forthabove, only a relatively limited number of these high acid ionomericresins have recently become commercially available.

[0041] The high acid ionomeric resins available from Exxon under thedesignation Escor® and or lotek®, are somewhat similar to the high acidionomeric resins available under the Surlyn® trademark. However, sincethe Escor®/lotek® ionomeric resins are sodium or zinc salts ofpoly(ethylene-acrylic acid) and the Surlyn® resins are zinc, sodium,magnesium, etc. salts of poly(ethylene-methacrylic acid), distinctdifferences in properties exist.

[0042] Examples of the high acid methacrylic acid based ionomers foundsuitable for use in accordance with this invention include Surlyn® 8220and 8240 (both formerly known as forms of Surlyn® AD-8422), Surlyn 9220(zinc cation), Surlyn® SEP-503-1 (zinc cation), and Surlyn® SEP-503-2(magnesium cation). According to DuPont, all of these ionomers containfrom about 18.5 to about 21.5% by weight methacrylic acid.

[0043] More particularly, Surlyn® AD-8422 is currently commerciallyavailable from DuPont in a number of different grades (i.e., AD-8422-2,AD-8422-3, AD-8422-5, etc.) based upon differences in melt index.According to DuPont, Surlyn® 8422, which is believed recently to havebeen redesignated as 8220 and 8240, offers the following generalproperties when compared to Surlyn® 8920, the stiffest, hardest of allon the low acid grades (referred to as “hard” ionomers in U.S. Pat. No.4,884,814): TABLE 1 LOW ACID (15 wt % HIGH ACID Acid) (>20 wt % Acid)SURLYN ® SURLYN ® 8920 8422-2 SURLYN ® 8422-3 IONOMER Cation Na Na NaMelt Index 1.2 2.8 1.0 Sodium, Wt % 2.3 1.9 2.4 Base Resin MI 60 60 60MP¹, ° C. 88 86 85 FP¹, ° C. 47 48.5 45 COMPRESSION MOLDING² TensileBreak (psi) 4350 4190 5330 Yield (psi) 2880 3670 3590 Elongation (%) 315263 289 Flex Modulus (Kpsi) 53.2 76.4 88.3 Shore D Hardness 66 67 68

[0044] In comparing Surlyn® 8920 to Surlyn® 8422-2 and Surlyn® 8422-3,it is noted that the high acid Surlyn® 8422-2 and 8422-3 ionomers have ahigher tensile yield, lower elongation, slightly higher Shore D hardnessand much higher flexural modulus. Surlyn® 8920 contains 15 weightpercent methacrylic acid and is 59% neutralized with sodium.

[0045] In addition, Surlyn® SEP-503-1 (zinc cation) and Surlyn®SEP-503-2 (magnesium cation) are high acid zinc and magnesium versionsof the Surlyn® AD 8422 high acid ionomers. When compared to the Surlyn®AD 8422 high acid ionomers, the Surlyn SEP-503-1 and SEP-503-2 ionomerscan be defined as follows: Surlyn ® Ionomer Ion Melt IndexNeutralization % AD 8422-3 Na 1.0 45 SEP 503-1 Zn 0.8 38 SEP 503-2 Mg1.8 43

[0046] Furthermore, Surlyn® 8162 is a zinc cation ionomer resincontaining approximately 20% by weight (i.e. 18.5-21.5% weight)methacrylic acid copolymer that has been 30-70% neutralized. Surlyn®8162 is currently commercially available from DuPont.

[0047] Examples of the high acid acrylic acid based ionomers suitablefor use in the present invention also include the Escor® or lotek® highacid ethylene acrylic acid ionomers produced by Exxon such as Ex 1001,1002, 959, 960, 989, 990, 1003, 1004, 993, 994. In this regard, Escor®or lotek® 959 is a sodium ion neutralized ethylene-acrylic neutralizedethylene-acrylic acid copolymer. According to Exxon, loteks® 959 and 960contain from about 19.0 to about 21.0% by weight acrylic acid withapproximately 30 to about 70 percent of the acid groups neutralized withsodium and zinc ions, respectively. The physical properties of thesehigh acid acrylic acid based ionomers are as follows: TABLE 2 Exxon HighAcid Ionomers ESCOR ® ESCOR ® (IOTEK) (IOTEK) Property Ex 1001 Ex 1002959 Ex 1003 Ex 1004 960 Melt index, g/10 min. 1.0 1.6 2.1 1.1 2.0 1.8Cation Na Na Na Zn Zn Zn Melting Point, ° C. 83.7 83.7 — 82 82.5 79Vicat Softening 51.5 51.5 58 56 55 55 Point, ° C. Tensile @ Break 34.4MPa 31.7 MPa  34 MPa 24.8 MPa 20.6 MPa  24 MPa Elongation @ Break, % 341348 280 387 437 430 Hardness, Shore D 63 62 65 54 53 57 Flexural Modulus 365 MPa  380 MPa 480 MPa  147 MPa  130 MPa 170 MPa

[0048] TABLE 3 Additional Exxon High Acid Ionomers Property Unit EX 989EX 993 EX 994 EX 990 Melt Index g/10 min. 1.30 1.25 1.32 1.24 Moistureppm 482 214 997 654 Cation Type — Na Li K Zn M+ content by AAS wt % 2.740.87 4.54 0 Zn content by AAS wt % 0 0 0 3.16 Density kg/m³ 959 945 976977 Vicat softening point ° C. 52.5 51 50 55.0 Crystallization point °C. 40.1 39.8 44.9 54.4 Melting point ° C. 82.6 81.0 80.4 81.0 Tensile atyield MPa 23.8 24.6 22 16.5 Tensile at break MPa 32.3 31.1 29.7 23.8Elongation at break % 330 260 340 357 1% secant modulus MPa 389 379 312205 Flexural modulus MPa 340 368 303 183 Abrasion resistance mg 20.0 9.215.2 20.5 Hardness Shore D — 62 62.5 61 56 Zwick Rebound % 61 63 59 48

[0049] Furthermore, as a result of the development by the assignee ofthis application of a number of new high acid ionomers neutralized tovarious extents by several different types of metal cations, such as bymanganese, lithium, potassium, calcium and nickel cations, several newhigh acid ionomers and/or high acid ionomer blends besides sodium, zincand magnesium high acid ionomers or ionomer blends are now available forgolf ball cover production. It has been found that these new cationneutralized high acid ionomer blends produce inner cover layercompositions exhibiting enhanced hardness and resilience due tosynergies which occur during processing. Consequently, the metal cationneutralized high acid ionomer resins recently produced can be blended toproduce substantially higher C.O.R.'s than those produced by the lowacid ionomer inner cover compositions presently commercially available.

[0050] More particularly, several new metal cation neutralized high acidionomer resins have been produced by the inventor by neutralizing, tovarious extents, high acid copolymers of an alpha-olefin and an alpha,beta-unsaturated carboxylic acid with a wide variety of different metalcation salts. This discovery is the subject matter of U.S. applicationSer. No. 08/493,089, now U.S. Pat. No. 5,688,869, incorporated herein byreference. It has been found that numerous new metal cation neutralizedhigh acid ionomer resins can be obtained by reacting a high acidcopolymer (i.e. a copolymer containing greater than 16% by weight acid,preferably from about 17 to about 25 weight percent acid, and morepreferably about 20 weight percent acid), with a metal cation saltcapable of ionizing or neutralizing the copolymer to the extent desired(i.e. from about 10% to 90%).

[0051] The base copolymer is made up of greater than 16% by weight of analpha, beta-unsaturated carboxylic acid and an alpha-olefin. Optionally,a softening comonomer can be included in the copolymer. Generally, thealpha-olefin has from 2 to 10 carbon atoms and is preferably ethylene,and the unsaturated carboxylic acid is a carboxylic acid having fromabout 3 to 8 carbons. Examples of such acids include acrylic acid,methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid,maleic acid, fumaric acid, and itaconic acid, with acrylic acid beingpreferred.

[0052] The softening comonomer that can be optionally included in theinner cover layer for the golf ball of the invention may be selectedfrom the group consisting of vinyl esters of aliphatic carboxylic acidswherein the acids have 2 to 10 carbon atoms, vinyl ethers wherein thealkyl groups contains 1 to 10 carbon atoms, and alkyl acrylates ormethacrylates wherein the alkyl group contains 1 to 10 carbon atoms.Suitable softening comonomers include vinyl acetate, methyl acrylate,methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate,butyl methacrylate, or the like.

[0053] Consequently, examples of a number of copolymers suitable for useto produce the high acid ionomers included in the present inventioninclude, but are not limited to, high acid embodiments of anethylene/acrylic acid copolymer, an ethylene/methacrylic acid copolymer,an ethylene/itaconic acid copolymer, an ethylene/maleic acid copolymer,an ethylene/methacrylic acid/vinyl acetate copolymer, anethylene/acrylic acid/vinyl alcohol copolymer, etc. The base copolymerbroadly contains greater than 16% by weight unsaturated carboxylic acid,from about 39 to about 83% by weight ethylene and from 0 to about 40% byweight of a softening comonomer. Preferably, the copolymer containsabout 20% by weight unsaturated carboxylic acid and about 80% by weightethylene. Most preferably, the copolymer contains about 20% acrylic acidwith the remainder being ethylene.

[0054] Along these lines, examples of the preferred high acid basecopolymers which fulfill the criteria set forth above, are a series ofethylene-acrylic copolymers which are commercially available from TheDow Chemical Company, Midland, Michigan, under the Primacor®designation. These high acid base copolymers exhibit the typicalproperties set forth below in Table 4. TABLE 4 Typical Properties ofPrimacor Ethylene-Acrylic Acid Copolymers VICAT TENSILE FLEXURAL SOFTSHORE D PERCENT DENSITY MELT YD ST G/10 MODULUS PT HARDNESS GRADE ACIDG/CC INDEX MIN (PSI) (° PSI) (° C.) ASTM D-792 D-1238* D-630 D-790D-1525 D-2240 5980 20.0 0.958 300.0 — 4800 43 50 5990 20.0 0.955 1300.0650 40 42 5981 20.0 0.960 300.0 900 3200 46 48 5983 20.0 0.958 500.0 8503100 44 45 5991 20.0 0.953 2600.0 635 2600 38 40

[0055] Due to the high molecular weight of the Primacor® 5981 grade ofthe ethylene-acrylic acid copolymer, this copolymer is the morepreferred grade utilized in the invention.

[0056] The metal cation salts utilized in the invention are those saltswhich provide the metal cations capable of neutralizing, to variousextents, the carboxylic acid groups of the high acid copolymer. Theseinclude acetate, oxide or hydroxide salts of lithium, calcium, zinc,sodium, potassium, nickel, magnesium, and manganese.

[0057] Examples of such lithium ion sources are lithium hydroxidemonohydrate, lithium hydroxide, lithium oxide and lithium acetate.Sources for the calcium ion include calcium hydroxide, calcium acetateand calcium oxide. Suitable zinc ion sources are zinc acetate dihydrateand zinc acetate, a blend of zinc oxide and acetic acid. Examples ofsodium ion sources are sodium hydroxide and sodium acetate. Sources forthe potassium ion include potassium hydroxide and potassium acetate.Suitable nickel ion sources are nickel acetate, nickel oxide and nickelhydroxide. Sources of magnesium include magnesium oxide, magnesiumhydroxide, magnesium acetate. Sources of manganese include manganeseacetate and manganese oxide.

[0058] The new metal cation neutralized high acid ionomer resins areproduced by reacting the high acid base copolymer with various amountsof the metal cation salts above the crystalline melting point of thecopolymer, such as at a temperature from about 200° F. to about 500° F.,preferably from about 250° F. to about 350° F. under high shearconditions at a pressure of from about 10 psi to 10,000 psi. Other wellknown blending techniques may also be used. The amount of metal cationsalt utilized to produce the new metal cation neutralized high acidbased ionomer resins is the quantity which provides a sufficient amountof the metal cations to neutralize the desired percentage of thecarboxylic acid groups in the high acid copolymer. The extent ofneutralization is generally from about 10% to about 90%.

[0059] As indicated below in Table 5 and more specifically in Example 1in U.S. application Ser. No. 08/493,089, issued as U.S. Pat. No.5,688,869, a number of new types of metal cation neutralized high acidionomers can be obtained from the above indicated process. These includenew high acid ionomer resins neutralized to various extents withmanganese, lithium, potassium, calcium and nickel cations. In addition,when a high acid ethylene/acrylic acid copolymer is utilized as the basecopolymer component of the invention and this component is subsequentlyneutralized to various extents with the metal cation salts producingacrylic acid based high acid ionomer resins neutralized with cationssuch as sodium, potassium, lithium, zinc, magnesium, manganese, calciumand nickel, several new cation neutralized acrylic acid based high acidionomer resins are produced. TABLE 5 Wt % Shore D Formulation No. Wt-%Cation Salt Neutralization Melt Index C.O.R. Hardness  1 (NaOH) 6.9867.5 0.9 .804 71  2 (NaOH) 5.66 54.0 2.4 .808 73  3 (NaOH) 3.84 35.912.2 .812 69  4 (NaOH) 2.91 27.0 17.5 .812 (brittle)  5 (MnAc) 19.6 71.77.5 .809 73  6 (MnAc) 23.1 88.3 3.5 .814 77  7 (MnAc) 15.3 53.0 7.5 .81072  8 (MnAc) 26.5 106 0.7 .813 (brittle)  9 (LiOH) 4.54 71.3 0.6 .810 7410 (LiOH) 3.38 52.5 4.2 .818 72 11 (LiOH) 2.34 35.9 18.6 .815 72 12(KOH) 5.30 36.0 19.3 Broke 70 13 (KOH) 8.26 57.9 7.18 .804 70 14 (KOH)10.7 77.0 4.3 .801 67 15 (ZnAc) 17.9 71.5 0.2 .806 71 16 (ZnAc) 13.953.0 0.9 .797 69 17 (ZnAc) 9.91 36.1 3.4 .793 67 18 (HgAc) 17.4 70.7 2.8.814 74 19 (HgAc) 20.6 87.1 1.5 .815 76 20 (HgAc) 13.8 53.8 4.1 .814 7421 (CaAc) 13.2 69.2 1.1 .813 74 22 (CaAc) 7.12 34.9 10.1 .808 70Controls: 50/50 Blend of Ioteks ® 8000/7030 C.O.R. = 810/65 Shore DHardness DuPont High Acid Surlyn ® 8422 (Na) C.O.R. = 811/70 Shore DHardness DuPont High Acid Surlyn ® 8162 (Zn) C.O.R. = 807/65 Shore DHardness Exxon High Acid Iotek ® EX-960 (Zn) C.O.R. = 796/65 Shore DHardness 23 (HgO) 2.91 53.5 2.5 .813 24 (HgO) 3.85 71.5 2.8 .808 25(HgO) 4.76 89.3 1.1 .809 26 (HgO) 1.96 35.7 7.5 .815 Control forformulation 23-26 is 50/50 Iotek ® 8000/7030 C.O.R. = 814, Formulation26 C.O.R. was normalized to that control accordingly 27 (NiAc) 13.0461.1 0.2 .802 71 28 (NiAc) 10.71 48.9 0.5 .799 72 29 (NiAc) 8.26 36.71.8 .796 63 30 (NiAc) 5.66 24.4 7.5 .786 64 Control for Formulation No.27-30 is 50/50 Iotek 8000/7030, C.O.R. = .807

[0060] When compared to low acid versions of similar cation neutralizedionomer resins, the new metal cation neutralized high acid ionomerresins exhibit enhanced hardness, modulus and resiliencecharacteristics. These are properties that are particularly desirable ina number of thermoplastic fields, including the field of golf ballmanufacturing.

[0061] When utilized in the construction of the inner layer of amulti-layered golf ball, it has been found that the new acrylic acidbased high acid ionomers extend the range of hardness beyond thatpreviously obtainable while maintaining the beneficial properties (i.e.durability, click, feel, etc.) of the softer low acid ionomer coveredballs, such as balls produced utilizing the low acid ionomers disclosedin U.S. Pat. Nos. 4,884,814 and 4,911,451.

[0062] Moreover, as a result of the development of a number of newacrylic acid based high acid ionomer resins neutralized to variousextents by several different types of metal cations, such as manganese,lithium, potassium, calcium and nickel cations, several new ionomers orionomer blends are now available for production of an inner cover layerof a multi-layered golf ball. By using these high acid ionomer resins,harder, stiffer inner cover layers having higher C.O.R.s, and thuslonger distance, can be obtained.

[0063] More preferably, it has been found that when two or more of theabove-indicated high acid ionomers, particularly blends of sodium andzinc high acid ionomers, are processed to produce the covers ofmulti-layered golf balls, (i.e., the inner cover layer herein) theresulting golf balls will travel further than previously knownmulti-layered golf balls produced with low acid ionomer resin covers dueto the balls' enhanced coefficient of restitution values.

[0064] The low acid ionomers which may be suitable for use informulating the inner layer compositions of the second and thirdembodiments of the subject invention are ionic copolymers which are themetal, i.e., sodium, zinc, magnesium, etc., salts of the reactionproduct of an olefin having from about 2 to 8 carbon atoms and anunsaturated monocarboxylic acid having from about 3 to 8 carbon atoms.Preferably, the ionomeric resins are copolymers of ethylene and eitheracrylic or methacrylic acid. In some circumstances, an additionalcomonomer such as an acrylate ester (i.e., iso- or n-butylacrylate,etc.) can also be included to produce a softer terpolymer. Thecarboxylic acid groups of the copolymer are partially neutralized (i.e.,approximately 10-100%, preferably 30-70%) by the metal ions. Each of thelow acid ionomer resins which may be included in the inner layer covercompositions of the invention contains 16% by weight or less of acarboxylic acid.

[0065] The inner layer compositions include the low acid ionomers suchas those developed and sold by E.I. DuPont de Nemours & Company underthe trademark Surlyn® and by Exxon Corporation under the trademarkEscor® or trademark lotek®, or blends thereof.

[0066] The low acid ionomer resins available from Exxon under thedesignation Escor® and/or lotek®, are somewhat similar to the low acidionomeric resins available under the Surlyn® trademark. However, sincethe Escor®/lotek® ionomeric resins are sodium or zinc salts ofpoly(ethylene-acrylic acid) and the Surlyn® resins are zinc, sodium,magnesium, etc. salts of poly(ethylene-methacrylic acid), distinctdifferences in properties exist.

[0067] When utilized in the construction of the inner layer of amulti-layered golf ball, it has been found that the low acid ionomerblends extend the range of compression and spin rates beyond thatpreviously obtainable. More preferably, it has been found that when twoor more low acid ionomers, particularly blends of sodium and zincionomers, are processed to produce the covers of multi-layered golfballs, (i.e., the inner cover layer herein) the resulting golf ballswill travel further and at an enhanced spin rate than previously knownmulti-layered golf balls. Such an improvement is particularly noticeablein enlarged or oversized golf balls.

[0068] As shown in the Examples, use of an inner layer formulated fromblends of lower acid ionomers produces multi-layer golf balls havingenhanced compression and spin rates. These are the properties desired bythe more skilled golfer.

[0069] In one embodiment of the inner cover layer, a blend of high andlow acid ionomer resins is used. These can be the ionomer resinsdescribed above, combined in a weight ratio which preferably is withinthe range of 10-90 to 90-10 high and low acid ionomer resins.

[0070] Another embodiment of the inner cover layer is primarily or fullynon-ionomeric thermoplastic material. Suitable non-ionomeric materialsinclude metallocene catalyzed polyolefins or polyamides,polyamidefionomer blends, polyphenylene ether/ionomer blends, etc.,which have a Shore D hardness of at least 60 and a flex modulus ofgreater than about 30,000 psi, or other hardness and flex modulus valueswhich are comparable to the properties of the ionomers described above.Other suitable materials include but are not limited to thermoplastic orthermosetting polyurethanes, thermoplastic block polyesters, e.g., apolyester elastomer such as that marketed by DuPont under the trademarkHytrel®, or thermoplastic block polyamides, e.g., a polyether amide suchas that marketed by Elf Atochem S.A. under the trademark Pebax®, a blendof two or more non-ionomeric thermoplastic elastomers, or a blend of oneor more ionomers and one or more non-ionomeric thermoplastic elastomers.These materials can be blended with the ionomers described above inorder to reduce cost relative to the use of higher quantities ofionomer.

[0071] Outer Cover Layer

[0072] While the core with the hard inner cover layer formed thereonprovides the multi-layer golf ball with power and distance, the outercover layer 16 is comparatively softer than the inner cover layer. Thesoftness provides for the feel and playability characteristics typicallyassociated with balata or balata-blend balls. The outer cover layer orply is comprised of a relatively soft, low modulus (about 1,000 psi toabout 10,000 psi) and, in one embodiment, low acid (less than 16 weightpercent acid) ionomer, an ionomer blend, a non-ionomeric thermoplasticor thermosetting material such as, but not limited to, a metallocenecatalyzed polyolefin such as Exact® material available from Exxon®, athermoplastic or thermoset polyurethane, thermoplastic block polyesters,e.g., a polyester elastomer such as that marketed by DuPont under thetrademark Hytrel®, or thermoplastic block polyamides, such as apolyether amide such as that marketed by Elf Atochem S.A. under thetrademark Pebax®, a blend of two or more non-ionomeric thermoplastic orthermosetting materials, or a blend of one or more ionomers and one ormore non-ionomeric thermoplastic materials. The outer layer is 0.010 toabout 0.15 inches in thickness, preferably 0.01-0.10 inches inthickness, more desirably 0.03 to 0.06 inches in thickness for a 1.680inch ball and 0.04 to 0.07 inches in thickness for a 1.72 inch or moreball), but thick enough to achieve desired playability characteristicswhile minimizing expense. Thickness is defined as the average thicknessof the non-dimpled areas of the outer cover layer. The outer cover layer16 has a Shore D hardness of 55 or less, and more preferably 50 or less.

[0073] In one embodiment, the outer cover layer preferably is formedfrom an ionomer which constitutes at least 75 weight % of an acrylateester-containing ionic copolymer or blend of acrylate ester-containingionic copolymers. This type of outer cover layer in combination with thecore and inner cover layer described above results in golf ball covershaving a favorable combination of durability and spin rate. The one ormore acrylate ester-containing ionic copolymers each contain an olefin,an acrylate ester, and an acid. In a blend of two or more acrylateester-containing ionic copolymers, each copolymer may contain the sameor a different olefin, acrylate ester and acid than are contained in theother copolymers. Preferably, the acrylate ester-containing ioniccopolymer or copolymers are terpolymers, but additional monomers can becombined into the copolymers if the monomers do not substantially reducethe scuff resistance or other good playability properties of the cover.

[0074] For a given copolymer, the olefin is selected from the groupconsisting of olefins having 2 to 8 carbon atoms, including, asnon-limiting examples, ethylene, propylene, butene-1, hexene-1 and thelike. Preferably the olefin is ethylene.

[0075] The acrylate ester is an unsaturated monomer having from 1 to 21carbon atoms which serves as a softening comonomer. The acrylate esterpreferably is methyl, ethyl, n-propyl, n-butyl, n-octyl, 2-ethylhexyl,or 2-methoxyethyl 1-acrylate, and most preferably is methyl acrylate orn-butyl acrylate. Another suitable type of softening comonomer is analkyl vinyl ether selected from the group consisting of n-butyl,n-hexyl, 2-ethylhexyl, and 2-methoxyethyl vinyl ethers.

[0076] The acid is a mono- or dicarboxylic acid and preferably isselected from the group consisting of methacrylic, acrylic, ethacrylic,α-chloroacrylic, crotonic, maleic, fumaric, and itaconic acid, or thelike, and half esters of maleic, fumaric and itaconic acid, or the like.The acid group of the copolymer is 10-100% neutralized with any suitablecation, for example, zinc, sodium, magnesium, lithium, potassium,calcium, manganese, nickel, chromium, tin, aluminum, or the like. It hasbeen found that particularly good results are obtained when theneutralization level is about 50-100%.

[0077] The one or more acrylate ester-containing ionic copolymers eachhas an individual Shore D hardness of about 5-64. The overall Shore Dhardness of the outer cover is 55 or less, and generally is 40-55. It ispreferred that the overall Shore D hardness of the outer cover is in therange of 40-50 in order to impart particularly good playabilitycharacteristics to the ball.

[0078] The outer cover layer of the invention is formed over a core toresult in a golf ball having a coefficient of restitution of at least0.770, more preferably at least 0.780, and most preferably at least0.790. The coefficient of restitution of the ball will depend upon theproperties of both the core and the cover. The PGA compression of thegolf ball is 100 or less, and preferably is 90 or less.

[0079] The acrylate ester-containing ionic copolymer or copolymers usedin the outer cover layer can be obtained by neutralizing commerciallyavailable acrylate ester-containing acid copolymers such aspolyethylene-methyl acrylate-acrylic acid terpolymers, including Escor®ATX (Exxon Chemical Company) or poly (ethylene-butylacrylate-methacrylic acid) terpolymers, including Nucrel® (DuPontChemical Company). Particularly preferred commercially availablematerials include ATX 320, ATX 325, ATX 310, ATX 350, and blends ofthese materials with Nucrel® 010 and Nucrel® 035. The acid groups ofthese materials and blends are neutralized with one or more of variouscation salts including zinc, sodium, magnesium, lithium, potassium,calcium, manganese, nickel, etc. The degree of neutralization rangesfrom 10-100%. Generally, a higher degree of neutralization results in aharder and tougher cover material. The properties of non-limitingexamples of commercially available un-neutralized acid terpolymers whichcan be used to form the golf ball outer cover layers of the inventionare provided below in Table 6. TABLE 6 Melt Index Flex modulus dg/minAcid No. MPa Hardness Trade Name ASTM D1238 % KOH/g (ASTM D790) (ShoreD) ATX 310 6 45 80 44 ATX 320 5 45 50 34 ATX 325 20 45 9 30 ATX 350 6 1520 28 Nucrel ® 010 11 60 40 40 Nucrel ® 035 35 60 59 40

[0080] The ionomer resins used to form the outer cover layers can beproduced by reacting the acrylate ester-containing acid copolymer withvarious amounts of the metal cation salts at a temperature above thecrystalline melting point of the copolymer, such as a temperature fromabout 200° F. to about 500° F., preferably from about 250° F. to about350° F., under high shear conditions at a pressure of from about 100 psito 10,000 psi. Other well known blending techniques may also be used.The amount of metal cation salt utilized to produce the neutralizedionic copolymers is the quantity which provides a sufficient amount ofthe metal cations to neutralize the desired percentage of the carboxylicacid groups in the high acid copolymer. When two or more differentcopolymers are to be used, the copolymers can be blended before or afterneutralization. Generally, it is preferable to blend the copolymersbefore they are neutralized to provide for optimal mixing.

[0081] The compatibility of the acrylate ester-containing copolymerswith each other in a copolymer blend produces a golf ball outer coverlayer having a surprisingly good scuff resistance for a given hardnessof the outer cover layer. The golf ball according to the invention has ascuff resistance of no higher than 3.0. It is preferred that the golfball has a scuff resistance of no higher than about 2.5 to ensure thatthe golf ball is scuff resistant when used in conjunction with a varietyof types of clubs, including sharp-grooved irons, which are particularlyinclined to result in scuffing of golf ball covers. The best resultsaccording to the invention are obtained when the outer cover layer has ascuff resistance of no more than about 2.0. The scuff resistance test isdescribed in detail below.

[0082] Additional materials may also be added to the inner and outercover layer of the present invention as long as they do notsubstantially reduce the playability properties of the ball. Suchmaterials include dyes (for example, Ultramarine Blue™ sold by Whitaker,Clark, and Daniels of South Plainsfield, N.J.) (see U.S. Pat. No.4,679,795); pigments such as titanium dioxide, zinc oxide, bariumsulfate and zinc sulfate; UV absorbers; antioxidants; antistatic agents;and stabilizers. Moreover, the cover compositions of the presentinvention may also contain softening agents such as those disclosed inU.S. Pat. Nos. 5,312,857 and 5,306,760, including plasticizers, metalstearates, processing acids, etc., and reinforcing materials such asglass fibers and inorganic fillers, as long as the desired propertiesproduced by the golf ball covers of the invention are not impaired.

[0083] The outer layer in another embodiment of the invention includes ablend of a soft (low acid) ionomer resin with a small amount of a hard(high acid) ionomer resin. A low modulus ionomer suitable for use in theouter layer blend has a flexural modulus measuring from about 1,000 toabout 10,000 psi, with a hardness of about 20 to about 40 on the Shore Dscale. A high modulus ionomer herein is one which measures from about15,000 to about 70,000 psi as measured in accordance with ASTM methodD-790. The hardness may be defined as at least 50 on the Shore D scaleas measured in accordance with ASTM method D-2240.

[0084] Soft ionomers primarily are used in formulating the hard/softblends of the cover compositions. These ionomers include acrylic acidand methacrylic acid based soft ionomers. They are generallycharacterized as comprising sodium, zinc, or other mono- or divalentmetal cation salts of a terpolymer of an olefin having from about 2 to 8carbon atoms, methacrylic acid, acrylic acid, or another α,β-unsaturated carboxylic acid, and an unsaturated monomer of theacrylate ester class having from 1 to 21 carbon atoms. The soft ionomeris preferably made from an acrylic acid base polymer in an unsaturatedmonomer of the acrylate ester class.

[0085] Certain ethylene-acrylic acid based soft ionomer resins developedby the Exxon Corporation under the designation lotek® 7520 (referred toexperimentally by differences in neutralization and melt indexes as LDX195, LDX 196, LDX 218 and LDX 219) may be combined with known hardionomers such as those indicated above to produce the inner and outercover layers. The combination produces higher C.O.R.s at equal or softerhardness, higher melt flow (which corresponds to improved, moreefficient molding, i.e., fewer rejects) as well as significant costsavings versus the outer layer of multi-layer balls produced by otherknown hard-soft ionomer blends as a result of the lower overall rawmaterials costs and improved yields.

[0086] Test data collected indicates that lotek® 7520 resins have ShoreD hardnesses of about 32 to 36 (per ASTM D-2240), melt flow indexes of3±0.5 g/10 min (at 190° C. per ASTM D-1288), and a flexural modulus ofabout 2500-3500 psi (per ASTM D-790). Furthermore, testing by anindependent testing laboratory by pyrolysis mass spectrometry indicatesthat lotek® 7520 resins are generally zinc salts of a terpolymer ofethylene, acrylic acid, and methyl acrylate.

[0087] Furthermore, it has been found that a grade of an acrylic acidbased soft ionomer available from the Exxon Corporation under thedesignation lotek® 7510 is also effective when combined with the hardionomers indicated above in producing golf ball covers exhibiting higherC.O.R. values at equal or softer hardness than those produced by knownhard-soft ionomer blends. In this regard, lotek® 7510 has the advantages(i.e. improved flow, higher C.O.R. values at equal hardness, increasedclarity, etc.) produced by the lotek® 7520 resin when compared to themethacrylic acid base soft ionomers known in the art (such as theSurlyn® 8625 and the Surlyn® 8629 combinations disclosed in U.S. Pat.No. 4,884,814).

[0088] In addition, lotek® 7510, when compared to lotek® 7520, producesslightly higher C.O.R. values at equal softness/hardness due to thelotek® 7510's higher hardness and neutralization. Similarly, lotek® 7510produces better release properties (from the mold cavities) due to itsslightly higher stiffness and lower flow rate than lotek® 7520. This isimportant in production where the soft covered balls tend to have loweryields caused by sticking in the molds and subsequent punched pin marksfrom the knockouts.

[0089] According to Exxon, lotek® 7510 is of similar chemicalcomposition as lotek® 7520 (i.e. a zinc salt of a terpolymer ofethylene, acrylic acid, and methyl acrylate) but is more highlyneutralized. Based upon FTIR analysis, lotek® 7520 is estimated to beabout 30-40 wt.-% neutralized and lotek® 7510 is estimated to be about40-60 wt.-% neutralized. The typical properties of lotek® 7510 incomparison of those of lotek® 7520 in comparison of those of lotek® 7520are set forth below: TABLE 7 Physical Properties of Iotek ® 7510 inComparison to Iotek ® 7520 Property Unit Iotek ® 7520 Iotek ® 7510 MeltIndex g/10 min. 2.0 0.8 Density g/cc 0.96 0.97 Melting Point ° F. 151149 Vicat Softening ° F. 108 109 Point Flex Modulus psi 3800 5300Tensile Strength psi 1450 1750 Elongation % 760 690 Hardness, Shore D —32 35

[0090] The hard ionomer resins utilized to produce the outer cover layercomposition hard/soft blends include ionic copolymers which are thesodium, zinc, magnesium, lithium, etc. salts of the reaction product ofan olefin having from 2 to 8 carbon atoms and an unsaturatedmonocarboxylic acid having from 3 to 8 carbon atoms. The carboxylic acidgroups of the copolymer may be totally or partially (i.e. approximately15-75 percent) neutralized.

[0091] The hard ionomeric resins are likely copolymers of ethylene andacrylic and/or methacrylic acid, with copolymers of ethylene and acrylicacid being the most preferred. Two or more types of hard ionomericresins may be blended into the outer cover layer compositions in orderto produce the desired properties of the resulting golf balls.

[0092] As discussed earlier herein, the hard ionomeric resins introducedunder the designation Escor® and sold under the designation lotek® aresomewhat similar to the hard ionomeric resins sold under the Surlyn®trademark. However, since the lotek® ionomeric resins are sodium or zincsalts of poly(ethylene-acrylic acid) and the Surlyn® resins are zinc orsodium salts of poly(ethylene-methacrylic acid) some distinctdifferences in properties exist. As more specifically indicated in thedata set forth below, the hard lotek® resins (i.e., the acrylic acidbased hard ionomer resins) are the more preferred hard resins for use informulating the layer blends for use in the present invention. Inaddition, various blends of lotek® and Surlyn® hard ionomeric resins, aswell as other available ionomeric resins, may be utilized in the presentinvention in a similar manner.

[0093] Examples of commercially available hard ionomeric resins whichmay be used in the present invention in formulating the outer coverblends include the hard sodium ionic copolymer sold under the trademarkSurlyn® 8940 and the hard zinc ionic copolymer sold under the trademarkSurlyn® 9910. Surlyn® 8940 is a copolymer of ethylene with methacrylicacid and about 15 weight percent acid which is about 29 percentneutralized with sodium ions. This resin has an average melt flow indexof about 2.8. Surlyn® 9910 is a copolymer of ethylene and methacrylicacid with about 15 weight percent acid which is about 58 percentneutralized with zinc ions. The average melt flow index of Surlyn® 9910is about 0.7. The typical properties of Surlyn® 9910 and 8940, as wellas other Surlyn® resins, are set forth below in Tables 8 and 9: TABLE 8Typical Properties of Commercially Available Hard Surlyn ® ResinsSuitable for Use in the Present Invention ASTM D 8940 9910 8920 85289970 9730 Cation type Sodium Zinc Sodium Sodium Zinc Zinc Melt flowindex, gms/10 min. D-1238 2.8 0.7 0.9 1.3 14.0 1.6 Specific gravity,g/cm³ D-792 0.95 0.97 0.95 0.94 0.95 0.95 Hardness, Shore D D-2240 65 6466 60 62 63 Tensile strength, (kpsi) D-638 (4.8) (3.6) (5.4) (4.2) (3.2)(4.1) MPa 33.1 24.8 37.2 29.0 22.1 28.3 Elongation, % D-638 470 290 350450 460 460 Flexural Modulus, (kpsi) D-790 (51) (48) (55) (32) (28) (30)MPa 350 330 380 220 190 210 Tensile Impact (23° C.), D-1822S 1020 1020865 1160 760 1240 KJ/m² (ft-lbs./in²) (485) (485) (410) (550) (360)(590) Vicat Temperature, ° C. D-1525 63 62 58 73 61 73

[0094] TABLE 9 Properties of Additional Hard Surlyn ® Resins SURLYN ®SURLYN ® SURLYN ® Ionomer 8920 8140 9120 Cation Na Na Na Melt Flow Indexgms/ 0.9 2.6 1.3 10 min. MP ° C. 84 88 85 FP ° C. 52 49 50 TensileStrength kpsi 5.4 5.0 3.8 Yield Strength kpsi 2.2 2.8 2.4 Elongation %350 340 280 Flex Modulus kpsi 55 71 64 Shore D Hardness 66 70 69

[0095] Examples of the more pertinent acrylic acid based hard ionomerresin suitable for use in the cover compositions sold under the lotek®tradename by the Exxon Corporation include lotek®, but are not limitedto, 8000, 8010, 8020, 8030, 7030, 7010, 7020, EX 1001-1009, lotek® 959and lotek® 960, as well as the materials listed above on Tables 2 and 3.The typical properties of the remainder of these and other lotek®ionomers suited for use in formulating the cover compositions are setforth below in Tables 10 and 11: TABLE 10 Typical Properties of Iotek ®Ionomers ASTM Resin Properties Method Units 7010 7020 7030 8000 80208030 Cation type zinc zinc zinc sodium sodium sodium Melt Index D-1238g/10 min 0.8 1.5 2.5 0.8 1.6 2.8 Density D-1505 kg/m3 968 966 964 957956 956 Melting Point D-3417 ° C. 83.5 84 85 83 84 87 CrystallizationD-3417 ° C. 55 56 58 45 47 49 Point Vicat Softening D-1525 ° C. 60 60 6054 54.5 55.5 Point Tensile strength D-638 MPa 24.5 23.5 22.6 33 32.5 32at break Yield Strength D-638 MPa 14 13 12 19 18.5 18 Elongation atD-638 % 440 450 460 370 380 410 break 1% Secant D-638 MPa 150 135 125280 280 280 Modulus Shore Hardness, D D-2240 — 54 53 52 60 60 60 FlexModulus D-790 MPa 190 175 155 320 340 355 (3 mm)

[0096] TABLE 11 Additional Examples of Exxon Ionomers PROPERTY Ex1005Ex1006 Ex1007 Ex1008 Ex1009 7310 Melt Index, 0.7 1.3 1.0 1.4 0.8 1.0g/10 min. Cation Na Na Zn Zn Na Zn Melting Point, 85.3 86 85.8 86 91.391 ° C. Vicat 54 57 60.5 60 56 69 Softening Point, ° C. Tensile @ break,33.9 33.5 24.1 23.6 32.4 24 MPa Elongation 403 421 472 427 473 520 @Break, % Hardness, 58 58 51 50 56 52 Shore D Flexural 289 290 152 141282 150 Modulus, MPa

[0097] It has been determined that when hard/soft ionomer blends areused for the outer cover layer, good results are achieved when therelative combination is in a range of about 3-25 percent hard ionomerand about 75-97 percent soft ionomer.

[0098] Moreover, in alternative embodiments, either the inner and/or theouter cover layer may also comprise up to 100 wt % of a soft, lowmodulus, non-ionomeric thermoplastic or thermoset material.Non-ionomeric materials are suitable so long as they produce theplayability and durability characteristics desired without adverselyaffecting the enhanced travel distance characteristic produced by thehigh acid ionomer resin composition. These include but are not limitedstyrene-butadiene-styrene block copolymers, including functionalizedstyrene-butadiene-styrene block copolymers,styrene-ethylene-butadiene-styrene (SEBS) block copolymers such asKraton® materials from Shell Chem. Co., and functionalized SEBS blockcopolymers; metallocene catalyzed polyolefins; ionomer/rubber blendssuch as those in Spalding U.S. Pat. Nos. 4,986,545; 5,098,105 and5,187,013; and, Hytrel® polyester elastomers from DuPont and Pebax®polyetheramides from Elf Atochem S.A.

[0099] A preferred non-ionomeric material suitable for the inner and/orouter cover layer includes polyurethane. Polyurethanes are polymerswhich are used to form a broad range of products. They are generallyformed by mixing two primary ingredients during processing. For the mostcommonly used polyurethanes, the two primary ingredients are apolyisocyanate (for example, diphenylmethane diisocyanate monomer(“MDI”) and toluene diisocyanate (“TDI”) and their derivatives) and apolyol (for example, a polyester polyol or a polyether polyol).

[0100] A wide range of combinations of polyisocyanates and polyols, aswell as other ingredients, are available. Furthermore, the end-useproperties of polyurethanes can be controlled by the type ofpolyurethane utilized, i.e., whether the material is thermoset (crosslinked molecular structure) or thermoplastic (linear molecularstructure).

[0101] Cross linking occurs between the isocyanate groups (—NCO) and thepolyol's hydroxyl end-groups (—OH). Additionally, the end-usecharacteristics of polyurethanes can also be controlled by differenttypes of reactive chemicals and processing parameters. For example,catalysts are utilized to control polymerization rates. Depending uponthe processing method, reaction rates can be very quick (as in the casefor some reaction injection molding systems (i.e., “RIM”) or may be onthe order of several hours or longer (as in several coating systems).Consequently, a great variety of polyurethanes are suitable fordifferent end-uses.

[0102] Polyurethanes are typically classified as thermosetting orthermoplastic. A polyurethane becomes irreversibly “set” when apolyurethane prepolymer is cross linked with a polyfunctional curingagent, such as a polyamine or a polyol. The prepolymer typically is madefrom polyether or polyester. Diisocyanate polyethers are preferredbecause of their water resistance.

[0103] The physical properties of thermoset polyurethanes are controlledsubstantially by the degree of cross linking. Tightly cross linkedpolyurethanes are fairly rigid and strong. A lower amount of crosslinking results in materials that are flexible and resilient.Thermoplastic polyurethanes have some cross linking, but primarily byphysical means. The crosslinkings bonds can be reversibly broken byincreasing temperature, as occurs during molding or extrusion. In thisregard, thermoplastic polyurethanes can be injection molded, andextruded as sheet and blow film. They can be used up to about 350° F.and are available in a wide range of hardnesses.

[0104] Polyurethane materials suitable for the present invention areformed by the reaction of a polyisocyanate, a polyol, and optionally oneor more chain extenders. The polyol component includes any suitablepolyether- or polyesterpolyol. Additionally, in an alternativeembodiment, the polyol component is polybutadiene diol. The chainextenders include, but are not limited, to diols, triols and amineextenders. Any suitable polyisocyanate may be used to form apolyurethane according to the present invention. The polyisocyanate ispreferably selected from the group of diisocyanates including, but notlimited, to 4,4′-diphenylmethane diisocyanate (“MDI”); 2,4-toluenediisocyanate (“TDI”); m-xylylene diisocyanate (“XDI”); methylenebis-(4-cyclohexyl isocyanate) (“HMDI”); hexamethylene diisocyanate(HDI); naphthalene-1,5,-diisocyanate (“NDI”);3,3′-dimethyl-4,4′-biphenyl diisocyanate (“TODI”); 1,4-diisocyanatebenzene (“PPDI”); phenylene-1,4-diisocyanate; and 2,2,4- or2,4,4-trimethyl hexamethylene diisocyanate (“TMDI”).

[0105] Other less preferred diisocyanates include, but are not limitedto, isophorone diisocyanate (“IPDI”); 1,4-cyclohexyl diisocyanate(“CHDI”); diphenylether4,4′-diisocyanate; p,p′-diphenyl diisocyanate;lysine diisocyanate (“LDI”); 1,3-bis (isocyanato methyl) cyclohexane;and polymethylene polyphenyl isocyanate (“PMDI”).

[0106] One polyurethane component which can be used in the presentinvention incorporates TMXDI (“META”) aliphatic isocyanate (CytecIndustries, West Paterson, N.J.). Polyurethanes based onmeta-tetramethylxylylene diisocyanate (TMXDI) can provide improved glossretention UV light stability, thermal stability, and hydrolyticstability. Additionally, TMXDI (“META”) aliphatic isocyanate hasdemonstrated favorable toxicological properties. Furthermore, because ithas a low viscosity, it is usable with a wider range of diols (topolyurethane) and diamines (to polyureas). If TMXDI is used, ittypically, but not necessarily, is added as a direct replacement forsome or all of the other aliphatic isocyanates in accordance with thesuggestions of the supplier. Because of slow reactivity of TMXDI, it maybe useful or necessary to use catalysts to have practical demoldingtimes. Hardness, tensile strength and elongation can be adjusted byadding further materials in accordance with the supplier's instructions.

[0107] The polyurethane which is selected for use as a golf ball coverpreferably has a Shore D hardness of from about 10 to about 55, morepreferably from about 30 to about 55, and most preferably from about 30to about 53 for a soft cover layer.

[0108] The polyurethane which is to be used for a cover layer preferablyhas a flex modulus from about 1 to about 310 Kpsi, more preferably fromabout 5 to about 100 Kpsi, and most preferably from about 5 to about 20Kpsi for a soft cover layer and 30 to 70 Kpsi for a hard cover layer.Accordingly, covers comprising these materials exhibit similarproperties.

[0109] A non-limiting example of a polyurethane suitable for use in theouter cover layer includes a polyester polyurethane such as B.F.Goodrich Company's Estane polyester polyurethane X4517. Thenon-ionomeric thermoplastic material may be blended with a soft ionomer.For example, polyamides blend well with soft ionomer. According to B.F.Goodrich, Estane® X4517 has the following properties: TABLE 12Properties of Estane ® X-4517 Tensile 1430 100% 815 200% 1024 300% 1193Elongation 641 Youngs Modulus 1826 Hardness A/D 88/39 Bayshore Rebound59 Solubility in Water Insoluble Melt processing temperature >350° F.(>177° C.) Specific Gravity (H₂O = 1) 1.1-1.3

[0110] Other soft, relatively low modulus non-ionomeric thermoplastic orthermoset polyurethanes may also be utilized to produce the inner and/orouter cover layers as long as the non-ionomeric materials produce theplayability and durability characteristics desired without adverselyaffecting the enhanced travel distance characteristic produced by thehigh acid ionomer resin composition. These include, but are not limitedto thermoplastic polyurethanes such as Texin® thermoplasticpolyurethanes from Mobay Chemical Co. and the Pellethane® thermoplasticpolyurethanes from Dow Chemical Co.; and non-ionomeric thermosetpolyurethanes including but not limited to those disclosed in U.S. Pat.5,334,673.

[0111] Other suitable polyurethane materials for use in the presentinvention golf balls include reaction injection molded (“RIM”)polyurethanes. RIM is a process by which highly reactive liquids areinjected into a closed mold, mixed usually by impingement and/ormechanical mixing in an in-line device such as a “peanut mixer,” wherethey polymerize primarily in the mold to form a coherent, one-piecemolded article. The RIM process usually involves a rapid reactionbetween one or more reactive components such as polyether- orpolyester-polyol, polyamine, or other material with an active hydrogen,and one or more isocyanate-containing constituents, often in thepresence of a catalyst. The constituents are stored in separate tanksprior to molding and may be first mixed in a mix head upstream of a moldand then injected into the mold. The liquid streams are metered in thedesired weight to weight ratio and fed into an impingement mix head,with mixing occurring under high pressure, e.g., 1,500 to 3,000 psi. Theliquid streams impinge upon each other in the mixing chamber of the mixhead and the mixture is injected into the mold. One of the liquidstreams typically contains a catalyst for the reaction. The constituentsreact rapidly after mixing to gel and form polyurethane polymers.Polyureas, epoxies, and various unsaturated polyesters also can bemolded by RIM.

[0112] Non-limiting examples of suitable RIM systems for use in thepresent invention are Bayflex® elastomeric polyurethane RIM systems,Baydur® GS solid polyurethane RIM systems, Prism® solid polyurethane RIMsystems, all from Bayer Corp. (Pittsburgh, Pa.), Spectrim® reactionmoldable polyurethane and polyurea systems from Dow Chemical USA(Midland, Mich.), including Spectrim® MM 373-A (isocyanate) and 373-B(polyol), and Elastolit® SR systems from BASF (Parsippany, N.J.).Preferred RIM systems include Bayflex® MP-10000 and Bayflex® 110-50,filled and unfilled. Further preferred examples are polyols, polyaminesand isocyanates formed by processes for recycling polyurethanes andpolyureas. Additionally, these various systems may be modified byincorporating a butadiene component in the diol agent.

[0113] A preferred form of the invention is a golf ball in which atleast one of the inner cover layer and/or the outer cover layercomprises a fast-chemical-reaction-produced component. This componentcomprises at least one material selected from the group consisting ofpolyurethane, polyurea, polyurethane ionomer, epoxy, and unsaturatedpolyesters, and preferably comprises polyurethane. A particularlypreferred form of the invention is a golf ball with a cover comprisingpolyurethane.

[0114] The method of the invention is particularly useful in forminggolf balls because it can be practiced at relatively low temperaturesand pressures. The preferred temperature range for the method of theinvention is from about 90 to about 180° F. when the component beingproduced contains polyurethane. Preferred pressures for practicing theinvention using polyurethane-containing materials are 200 psi or lessand more preferably 100 psi or less. The method of the present inventionoffers numerous advantages over conventional slow-reactive processcompression molding of golf ball covers. The method of the presentinvention results in molded covers in a demold time of 10 minutes orless, preferably 2 minutes or less, and most preferably in 1 minute orless. The method of the present invention results in the formation of areaction product formed by mixing two or more reactants together, thatexhibits a reaction time of about 2 minutes or less, preferably oneminute or less, and most preferably about 30 seconds or less. The termfast-chemical-reaction-produced component as used herein refers to suchreaction products. An excellent finish can be produced on the ballutilizing these components and molding techniques.

[0115] The polyol component typically contains additives, such asstabilizers, flow modifiers, catalysts, combustion modifiers, blowingagents, fillers, pigments, optical brighteners, and release agents tomodify physical characteristics of the cover. Polyurethane/polyureaconstituent molecules that were derived from recycled polyurethane canbe added in the polyol component.

[0116] A golf ball inner cover layer according to the present inventionformed from a polyurethane material typically contains from about 0 toabout 60 weight percent of filler material, more preferably from about 1to about 30 weight percent, and most preferably from about 1 to about 20weight percent.

[0117] A golf ball outer cover layer according to the present inventionformed from a polyurethane material typically contains from about 0 toabout 20 weight percent of filler material, more preferably from about 1to about 10 weight percent, and most preferably from about 1 to about 5weight percent.

[0118] Core

[0119] The cores of the inventive golf balls typically have acoefficient of restitution of about 0.750 or more, more preferably 0.770or more and a PGA compression of about 90 or less, and more preferably70 or less. Furthermore, in some applications it may be desirable toprovide a core with a coefficient of restitution of about 0.780 to 0.790or more. The core used in the golf ball of the invention preferably is asolid. The term “solid cores” as used herein refers not only to onepiece cores but also to those cores having a separate solid layerbeneath the covers and over the central core. The cores have a weight of25-40 grams and preferably 30-40 grams. When the golf ball of theinvention has a solid core, this core can be compression molded from aslug of uncured or lightly cured elastomer composition comprising a highcis content polybutadiene and a metal salt of an α, β, ethylenicallyunsaturated carboxylic acid such as zinc mono- or diacrylate ormethacrylate. To achieve higher coefficients of restitution and/or toincrease hardness in the core, the manufacturer may include a smallamount of a metal oxide such as zinc oxide. In addition, larger amountsof metal oxide than are needed to achieve the desired coefficient may beincluded in order to increase the core weight so that the finished ballmore closely approaches the U.S.G.A. upper weight limit of 1.620 ounces.Non-limiting examples of other materials which may be used in the corecomposition including compatible rubbers or ionomers, and low molecularweight fatty acids such as stearic acid. Free radical initiatorcatalysts such as peroxides are admixed with the core composition sothat on the application of heat and pressure, a curing or cross-linkingreaction takes place.

[0120] A thread wound core may comprise a liquid, solid, gel ormulti-piece center. The thread wound core is typically obtained bywinding a thread of natural or synthetic rubber, or thermoplastic orthermosetting elastomer such as polyurethane, polyester, polyamide, etc.on a solid, liquid, gel or gas filled center to form a thread rubberlayer that is then covered with one or more mantle or cover layers.Additionally, prior to applying the cover layers, the thread wound coremay be further treated or coated with an adhesive layer, protectivelayer, or any substance that may improve the integrity of the wound coreduring application of the cover layers and ultimately in usage as a golfball. Since the core material is not an integral part of the presentinvention, further detailed discussion concerning the specific types ofcore materials which may be utilized with the cover compositions of theinvention are not specifically set forth herein.

[0121] Since the core material is not an integral part of the presentinvention, a detailed discussion concerning the specific types of corematerials which may be utilized with the cover compositions of theinvention are not specifically set forth herein.

[0122] Method of Making Golf Ball

[0123] In preparing golf balls in accordance with the present invention,a hard inner cover layer is molded (for example, by injection molding orby compression molding) about a core (preferably a solid core). Acomparatively softer outer layer is molded over the inner layer.

[0124] The solid core for the multi-layer ball is about 1.2-1.6 inchesin diameter, although it may be possible to use cores in the range ofabout 1.0-2.0 inches. Conventional solid cores are typically compressionor injection molded from a slug or ribbon of uncured or lightly curedelastomer composition comprising a high cis content polybutadiene and ametal salt of an α, β, ethylenically unsaturated carboxylic acid such aszinc mono or diacrylate or methacrylate. To achieve higher coefficientsof restitution in the core, the manufacturer may include fillers such assmall amounts of a metal oxide such as zinc oxide. In addition, largeramounts of metal oxide than those that are needed to achieve the desiredcoefficient are often included in conventional cores in order toincrease the core weight so that the finished ball more closelyapproaches the U.S.G.A. upper weight limit of 1.620 ounces. Othermaterials may be used in the core composition including compatiblerubbers or ionomers, and low molecular weight fatty acids such asstearic acid. Free radical initiators such as peroxides are admixed withthe core composition so that on the application of heat and pressure, acomplex curing cross-linking reaction takes place.

[0125] The inner cover layer which is molded over the core is about 0.01inches to about 0.10 inches in thickness, preferably about 0.03-0.07inches thick. The inner ball which includes the core and inner coverlayer preferably has a diameter in the range of 1.25 to 1.60 inches. Theouter cover layer is about 0.01 inches to about 0.10 inches inthickness. Together, the core, the inner cover layer and the outer coverlayer combine to form a ball having a diameter of 1.680 inches or more,the minimum diameter permitted by the rules of the United States GolfAssociation and weighing no more than 1.62 ounces.

[0126] In a particularly preferred embodiment of the invention, the golfball has a dimple pattern which provides coverage of 65% or more. Thegolf ball typically is coated with a durable, abrasion-resistant,relatively non-yellowing finish coat if necessary.

[0127] The various cover composition layers of the present invention maybe produced according to conventional melt blending procedures.Generally, the copolymer resins are blended in a Banbury® type mixer,two-roll mill, or extruder prior to neutralization. After blending,neutralization then occurs in the melt or molten state in the Banbury®mixer. Mixing problems are minimal because preferably more than 75 wt %,and more preferably at least 80 wt % of the ionic copolymers in themixture contain acrylate esters, and in this respect, most of thepolymer chains in the mixture are similar to each other. The blendedcomposition is then formed into slabs, pellets, etc., and maintained insuch a state until molding is desired. Alternatively, a simple dry blendof the pelletized or granulated resins which have previously beenneutralized to a desired extent and colored master batch may be preparedand fed directly into the injection molding machine where homogenizationoccurs in the mixing section of the barrel prior to injection into themold. If necessary, further additives such as an inorganic filler, etc.,may be added and uniformly mixed before initiation of the moldingprocess. A similar process is utilized to formulate the high acidionomer resin compositions used to produce the inner cover layer. In oneembodiment of the invention, a master batch of non-acrylateester-containing ionomer with pigments and other additives incorporatedtherein is mixed with the acrylate ester-containing copolymers in aratio of about 1-7 weight % master batch and 93-99 weight % acrylateester-containing copolymer.

[0128] The golf balls of the present invention can be produced bymolding processes which include but are not limited to those which arecurrently well known in the golf ball art. For example, the golf ballscan be produced by injection molding or compression molding the novelcover compositions around a wound or solid molded core to produce aninner ball which typically has a diameter of about 1.50 to 1.67 inches.The outer layer is subsequently molded over the inner layer to produce agolf ball having a diameter of 1.620 inches or more, preferably about1.680 inches or more. Although either solid cores or wound cores can beused in the present invention, as a result of their lower cost andsuperior performance, solid molded cores are preferred overwound cores.The standards for both the minimum diameter and maximum weight of theballs are established by the United States Golf Association (U.S.G.A.).

[0129] In compression molding, the inner cover composition is formed viainjection at about 380° F. to about 450° F. into smooth surfacedhemispherical shells which are then positioned around the core in a moldhaving the desired inner cover thickness and subjected to compressionmolding at 200° to 300° F. for about 2 to 10 minutes, followed bycooling at 50° to 70° F. for about 2 to 7 minutes to fuse the shellstogether to form a unitary intermediate ball. In addition, theintermediate balls may be produced by injection molding wherein theinner cover layer is injected directly around the core placed at thecenter of an intermediate ball mold for a period of time in a moldtemperature of from 50° to about 100° F. Subsequently, the outer coverlayer is molded about the core and the inner layer by similarcompression or injection molding techniques to form a dimpled golf ballof a diameter of 1.680 inches or more.

[0130] After molding, the golf balls produced may undergo variousfurther processing steps such as buffing, painting and marking asdisclosed in U.S. Pat. No. 4,911,451.

[0131] The resulting golf ball produced from the hard inner layer andthe relatively softer, low flexural modulus outer layer provide for animproved multi-layer golf ball which provides for desirable coefficientof restitution and durability properties while at the same time offeringthe feel and spin characteristics associated with soft balata andbalata-like covers of the prior art.

[0132] Additionally, golf balls of the present invention that comprisepolyurethane in any of the inner and outer cover layer may be producedby a reaction injection molding process (RIM). RIM is a process by whichhighly reactive liquids are injected into a closed mold, mixed usuallyby impingement and/or mechanical mixing in an in-line device such as a“peanut mixer,” where they polymerize primarily in the mold to form acoherent, one-piece molded article. The RIM process usually involves arapid reaction between one or more reactive components such aspolyether- or polyester-polyol, polyamine, or other material with anactive hydrogen, and one or more isocyanate-containing constituents,often in the presence of a catalyst. The constituents are stored inseparate tanks prior to molding and may be first mixed in a mix headupstream of a mold and then injected into the mold. The reaction mixtureviscosity should be sufficiently low to ensure that the empty space inthe mold is completely filled. The reactant materials generally arepreheated to 90° F. to 150° F. before they are mixed. In most cases itis necessary to preheat the mold to, e.g., 100 to 180° F., to ensureproper injection viscosity. The liquid streams are metered in thedesired weight to weight ratio and fed into an impingement mix head,with mixing occurring under high pressure, e.g., 1,500 to 3,000 psi. Theliquid streams impinge upon each other in the mixing chamber of the mixhead and the mixture is injected into the mold. Injector nozzles impingethe isocyanate and polyol at ultra-high velocity to provide excellentmixing. Additional mixing may be conducted using an aftermixer, whichtypically is constructed inside the mold between the mix head and themold cavity. One of the liquid streams typically contains a catalyst forthe reaction. The constituents react rapidly after mixing to gel andform polyurethane polymers. Polyureas, epoxies, and various unsaturatedpolyesters also can be molded by RIM.

[0133] Golf balls and, more specifically, cover layers formed by RIM arepreferably formed by the process described in application Ser. No.09/040,798, filed Mar. 18, 1998, incorporated herein by reference.

[0134] RIM differs from non-reaction injection molding in a number ofways. The main distinction is that in RIM a chemical reaction takesplace in the mold to transform a monomer or adducts to polymers and thecomponents are in liquid form. Thus, a RIM mold need not be made towithstand the pressures which occur in a conventional injection molding.In contrast, injection molding is conducted at high molding pressures inthe mold cavity by melting a solid resin and conveying it into a mold,with the molten resin often being at about 150 to about 350° C. At thiselevated temperature, the viscosity of the molten resin usually is inthe range of about 50,000 to about 1,000,000 centipoise, and istypically around 200,000 centipoise. In an injection molding process,the solidification of the resins occurs after about 10 to about 90seconds, depending upon the size of the molded product, the temperatureand heat transfer conditions, and the hardness of the injection moldedmaterial. Subsequently, the molded product is removed from the mold.There is no significant chemical reaction taking place in an injectionmolding process when the thermoplastic resin is introduced into themold. In contrast, in a RIM process, the chemical reaction causes thematerial to set in less than about 5 minutes, often in less than 2minutes, preferably in less than one minute, more preferably in lessthan 30 seconds, and in many cases in about 10 seconds or less.

[0135] Catalysts can be added to the RIM polyurethane system startingmaterials as long as the catalysts generally do not react with theconstituent with which they are combined. Suitable catalysts includethose which are known to be useful with polyurethanes and polyureas.

[0136] The polyol component typically contains additives, such asstabilizers, flow modifiers, catalysts, combustion modifiers, blowingagents, fillers, pigments, optical brighteners, and release agents tomodify physical characteristics of the cover. Recycledpolyurethane/polyurea also can be added to the core.Polyurethane/polyurea constituent molecules that were derived fromrecycled polyurethane can be added in the polyol component.

[0137] The mold cavity contains retractable pins and is generallyconstructed in the same manner as a mold cavity used to injection mold athermoplastic, e.g., ionomeric golf ball cover. However, two differenceswhen RIM is used are that tighter pin tolerances generally are required,and a lower injection pressure is used. Also, the molds can be producedfrom lower strength material such as aluminum.

[0138] RIM may provide for improved cover layers. If plastic productsare produced by combining components that are preformed to some extent,subsequent failure can occur at a location on the cover which is alongthe seam or parting line of the mold. Failure can occur at this locationbecause this interfacial region is intrinsically different from theremainder of the cover layer and can be weaker or more stressed. Coverlayers produced via RIM are believed to provide for improved durabilityof a golf ball cover layer by providing a uniform or “seamless” cover inwhich the properties of the cover material in the region along theparting line are generally the same as the properties of the covermaterial at other locations on the cover, including at the poles. Theimprovement in durability is believed to be a result of the fact thatthe reaction mixture is distributed uniformly into a closed mold. Thisuniform distribution of the injected materials eliminates knit-lines andother molding deficiencies which can be caused by temperature differenceand/or reaction difference in the injected materials. RIM typicallyresults in generally uniform molecular structure, density and stressdistribution as compared to conventional injection-molding processes.

[0139] The golf balls formed according to the present invention can becoated using a conventional two-component spray coating or can be coatedduring the RIM process, i.e., using an in-mold coating process.

[0140] Unique Spin Characteristics

[0141] As indicated above, the golf balls of the invention are unique inthat they provide good distance when hit with a driver, good control offof irons, and excellent spin on short chip shots. This type of golf ballis superior to conventional soft covered two-piece or wound balls inthat it has lower spin off of a driver and higher spin on short shots.

[0142] The spin factor of the ball of the invention may be specified inthe manner described below.

[0143] Step 1. A golf ball testing machine is set up in order that itmeets the following conditions for hitting a 1995 Top-Flite® TourZ-balata 90 ball available from Spalding Sports Worldwide, Inc. ClubLaunch Angle Ball Speed Spin Rate 9 iron 21 ± 1.5 160.5 ± 9.0 9925 ± 600

[0144] The machine is set up such that the above conditions are met foreach test using 10 Z-balata 90 golf balls which are hit 3 times each atthe same machine setting. The thirty measurements of spin rate areaveraged to obtain N_(9I-ZB).

[0145] Step 2. Ten golf balls of the invention (Ball X) are hit 3 timeseach using the same machine setting as was used for the Z-balata ballsand spin data is collected. Any clearly erratic spin test result iseliminated and replaced by a new test with the same ball. The thirtymeasurements of spin rate are averaged to obtain N_(91-X).

[0146] Step 3. The machine is set up in order that it meets thefollowing conditions for hitting a 1995 Z-balata 90 ball, the conditionsbeing intended to replicate a 30-yard chip shot: Club Launch Angle BallSpeed Spin Rate Sand Wedge 28 ± 4.5 58.0 ± 4.0 4930 ± 770

[0147] The machine is set up such that the above conditions are met foreach test using 10 Z-balata 90 golf balls which are hit 3 times each atthe same machine setting. The thirty measurements of spin rate areaveraged to obtain N_(SW-ZB).

[0148] Step 4. The 10 golf balls used in Step 2 are hit three times eachusing the same machine setting as was used in Step 3 and spin data iscollected. Any clearly erratic spin test result is eliminated andreplaced by a new test with the same ball. The thirty measurements ofspin rate are averaged to obtain N_(SW-X).

[0149] Step 5. The numerical values of N_(9I-ZB), N_(91-X), N_(SW-ZB)and N_(SW-X) are inserted into the following formula to obtain a spinfactor:${{Spin}\quad {Factor}} = {\frac{M_{{SW} - X}}{N_{91 - X}} - {\frac{N_{{SW} - {ZB}}}{N_{91 - {ZB}}} \times 100}}$

[0150] The golf ball of the invention has a spin factor of 3.0 or more,more preferably 5.0 or more, and most preferably 8.0 or more.

[0151] The present invention is further illustrated by the followingexamples in which the parts of the specific ingredients are by weight.It is to be understood that the present invention is not limited to theexamples, and various changes and modifications may be made in theinvention without departing from the spirit and scope thereof.

EXAMPLE 1 Ionic Terpolymer-Containing Cover

[0152] A set of two-piece golf balls was made with solid cores and acover composition of 75 weight % Nucrel® 035, which is an acrylateester-containing acid terpolymer, and 25 weight % of a master batchcontaining 4.5 weight % MgO in Surlyn® 1605 (“MgO Master batch”). Theterpolymer was reacted with the master batch at a temperature of about250° F. under high shear conditions at a pressure of about 0 to 100 psi.The magnesium in the master batch neutralized acid groups of theterpolymer at a level of about 62% neutralization. The molded balls werefinished with polyurethane primer and top coats. The PGA compression,coefficient of restitution, Shore C hardness, scuff resistance, spinrate and cold crack of the golf balls were determined. The results areshown on Table 13 below.

[0153] To measure cold crack, the finished golf balls were stored at−10° F. for at least 24 hours and were then subjected to 5 blows in acoefficient machine at 165 ft/sec. The balls were allowed to return toroom temperature and were then visually inspected for cover cracking.None of the golf balls experienced cracking.

[0154] Coefficient of restitution (C.O.R.) was measured by firing theresulting golf ball in an air cannon at a velocity of 125 feet persecond against a steel plate which was positioned 12 feet from themuzzle of the cannon. The rebound velocity was then measured. Therebound velocity was divided by the forward velocity to give thecoefficient of restitution. Shore hardness was determined in generalaccordance with ASTM Test 2240, but was measured on a non-dimpled areaof the surface of the golf ball.

COMPARATIVE EXAMPLE 1 Ionic Copolymer Cover (Non-Terpolymer)

[0155] A set of 12 two-piece golf balls was made according to the sameprocedure as that of Example 1 with the exception that Nucrel® 925, anon-acrylate ester-containing acid copolymer was substituted for Nucrel®035. The resulting golf ball cover was too hard, resulting in fourbreaks during cold crack testing. The results are shown on Table 13.

COMPARATIVE EXAMPLE 2 Ionomer—Non-Ionic Terpolymer Blend

[0156] The procedure of Example 1 was repeated with the exception thatthe MgO Master batch was replaced by pure Surlyn® 1605. All of the golfball covers broke during cold crack testing. The results are shown onTable 13.

COMPARATIVE EXAMPLE 3 Ionomer—Non-Ionic Copolymer Blend

[0157] The procedure of Comparative Example 1 was repeated with theexception that the MgO master batch was replaced by pure Surlyn® 1605.The results are shown on Table 13. When subjected to cold crack testing,all of the golf ball covers broke.

[0158] As can be seen from the results of Example 1 and ComparativeExamples 1-3, inferior golf balls are obtained when a hard, non-acrylateester-containing copolymer is used instead of a softer, acrylateester-containing terpolymer, and when either an acrylateester-containing acid terpolymer or a non-acrylate ester-containing acidcopolymer is not neutralized with metal ions. TABLE 13 COR ExperimentCover PGA (× Shore C Cold No. Material Weight Comp. 1000) Hardness Crack1-1 75% Nucrel ® 035/ 45.2 104 .783 80 No breaks 25% MgO MB in Surlyn ®1605 Comp. 1 75% Nucrel ® 925/ 45.1 111 .798 90 4 breaks 25% MgO MB inSurlyn ® 1605 Comp. 2 75% Nucrel ® 035/ 45.1  99 .774 70 All broke 25%Surlyn ® 1605 Comp. 3 75% Nucrel ® 925/ 45.2 106 .790 75 All broke 25%Surlyn ® 1605

EXAMPLE 2 Ionic T rpolym rs

[0159] An acrylate ester-containing terpolymer sold as Escor® ATX 325(Exxon Chemical Co.) was 57% neutralized with lithium cations. Theionomeric material, which also contained titanium dioxide, brightener,etc. from a white master batch, was placed over a solid golf ball coreand the golf ball was primed and top coated. The properties of theresulting golf ball are shown on Table 14. This procedure was repeatedusing different combinations of terpolymers with cations and cationblends at the degrees of neutralization which are shown on Table 14. Inthe cation blends, mole ratios were about 1:1:1. All of the ATXmaterials shown on Table 14 are Escor® ATX materials available fromExxon Chemical Co. The Nucrel® materials are available from DuPontChemical Co. Primacor® 3440 is available from Dow Chemical Co.

[0160] The spin rate of the golf ball was measured by striking theresulting golf balls with a pitching wedge or 9-iron wherein theclub-head speed is about 80 feet per second and the ball was launched atan angle of 26 to 34 degrees with an initial velocity of 100-115 feetper second. The spin rate was measured by observing the rotation of theball in flight using stop action Strobe photography or via the use of ahigh speed video system.

[0161] The scuff resistance test was conducted in the following manner:a Top-Flite® tour pitching wedge (1994) with box grooves was obtainedand was mounted in a Miyamae® driving machine. The club face wasoriented for a square hit. The forward/backward tee position wasadjusted so that the tee was four inches behind the point in thedownswing where the club was vertical. The height of the tee and thetoe-heel position of the club relative to the tee were adjusted in orderthat the center of the impact mark was about ¾ of an inch above the soleand was centered toe to heel across the face. The machine was operatedat a club head speed of 125 feet per second. A minimum of three samplesof each ball were tested. Each ball was hit three times.

[0162] After testing, the balls were rated according to the followingtable: Rating Type of damage 1 Little or no damage (groove markings ordents) 2 Small cuts and/or ripples in cover 3 Moderate amount ofmaterial lifted from ball surface but still attached to ball 4 Materialremoved or barely attached

[0163] The balls that were tested were primed and top coated.

[0164] As shown on Table 14, many of the cover materials resulted ingolf balls having a scuff resistance of 1.5 or less, and others had ascuff resistance rating of 1.5-2.5.

COMPARATIVE EXAMPLE 4 Hard/Soft Ionomer Blend

[0165] A golf ball with a cover formed from a blend of a commerciallyavailable hard sodium ionomer and a commercially available soft acrylateester-containing zinc ionomer in which the blend contains less than 60wt % soft ionomer was subjected to the same testing as the golf balls ofExample 2. The results are shown on Table 14. TABLE 14 COR Spin RateExperiment % PGA (× Shore D Scuff (#9 Iron at No. Cover Material CationNeutralization Comp. 1000) Hardness Resist. 105 ft/sec) Comp. 4Hard-soft ionomer Zn/Na 60 90 787 58 4.0 9,859 blend 1 (control) 2-1 ATX325 Li 57 86 787 51 1.0 10,430 2-2 ATX 325 Li/Zn/K 65 86 787 50 1.010,464 2-3 ATX 320 Li 57 N.T. N.T. 56 1.0 10,299 2-4 ATX 320 Li/Zn/K 6587 790 55 1.5 10,355 2-5 Nucrel 010 Li — 89 803 65 3.0  7,644 2-6 Nucrel010 Li/Zn/K — 89 802 65 4.0  7,710 2-7 Nucrel 035 Li — 87 801 62 3.0 8,931 2-8 Nucrel 035 Li/Zn/K — 87 798 62 3.0  8,915 2-9 ATX 310 Li 5388 802 62 2.5  8,892 2-10 ATX 310 Li/Zn/K 60 88 801 63 2.5  8,244 2-11ATX 325 Li 57 83 797 55 1.5 — 2-12 ATX 325 Li/Zn/K 65 82 796 53 1.5 —2-13 50% ATX 325-Li Li 28.5 89 777 50 1.5 — 50% ATX 320- unneut. 2-1475% ATX320- Li/Zn/K 49 87 776 54 1.5 — Li/Zn/K 25% ATX320- unneut. 2-1560% ATX325 Li/Zn/K 39 88 779 54 1.5 — 40% Primacor 3440-unneut. 2-16 ATX320 Unneut. — 88 775 45 2.0 — 2-17 ATX 325 Unneut. — 88 — 42 1.5 — 2-18ATX 325 Li 50 95 795 50 1.0 — 2-19 ATX 325 Li 30 96 791 46 1.5 — 2-20ATX 325 Li/Zn/K 50 91 791 48 1.0 — 2-21 ATX 325 Li/Zn/K 30 90 N.T. 451.0 — 2-22 ATX 325 Li/Zn/K 50 91 N.T. 47 1.0 —

EXAMPLE 3 Ionic Terpolymers

[0166] The procedure of Example 2 was repeated with the exception thatsingle cations of lithium, magnesium, sodium and potassium were used inthe cover material. The results are shown on Table 15.

[0167] As indicated on Table 15, the scuff resistance of the golf ballswas 3.0 or better. The scuff resistance of the balls with covers made ofan acrylic acid terpolymer was 1.0. For a given terpolymer, the scuffresistance did not change when different cations were used forneutralization. TABLE 15 COR Experiment Cover PGA (× Shore D Scuff No.Material Cation % Neutralization Comp. 1000) Hardness Resistance 3-1Nucrel ® 035 Li 100 90 792 62 3.0 3-2 Nucrel ® 035 Mg 100 89 792 62 3.03-3 ATX 325 Li 100 86 790 51 1.0 3-4 ATX 325 Mg 100 85 791 51 1.0 3-5ATX 325 Na 81 85 790 51 1.0 3-6 ATX 325 K 95 85 791 51 1.0

COMPARATIVE EXAMPLE 5

[0168] Several intermediate balls (cores plus inner cover layers) wereprepared in accordance with conventional molding procedures describedabove. The inner cover compositions were molded around 1.545 inchdiameter cores weighing 36.5 grams with a specific gravity of about 1.17such that the inner cover had a wall thickness of about 0.0675 inchesand a specific gravity of about 0.95, with the overall ball measuringabout 1.680 inches in diameter.

[0169] The cores utilized in the examples were comprised of thefollowing ingredients: 100 parts by weight high cis-polybutadiene, 31parts by weight zinc diacrylate, about 6 parts by-weight zinc oxide, 20parts by weight zinc stearate, 17-18 parts by weight calcium carbonate,and small quantities of peroxide, coloring agent and a polymericisocyanate sold as Papi® 94 (Dow Chemical Co.). The molded coresexhibited PGA compressions of about 100 and C.O.R. values of about0.800.

[0170] The inner cover compositions designated herein as compositionsA-E utilized to formulate the intermediate balls are set forth in Table16 below. The resulting molded intermediate balls were tested todetermine the individual compression (Riehle), C.O.R., Shore C hardness,spin rate and cut resistance properties. These results are also setforth in Table 16 below.

[0171] The data of these examples are the average of twelve intermediateballs produced for each example. The properties were measured accordingto the following parameters:

[0172] Cut resistance was measured in accordance with the followingprocedure: A golf ball was fired at 135 feet per second against theleading edge of a pitching wedge wherein the leading edge radius is{fraction (1/32)} inch, the loft angle is 51 degrees, the sole radius is2.5 inches and the bounce angle is 7 degrees.

[0173] The cut resistance of the balls tested herein was evaluated on ascale of 1 to 5. The number 1 represents a cut that extends completelythrough the cover to the core. A 2 represents a cut that does not extendcompletely through the cover but that does break the surface. A 3 doesnot break the surface of the cover but does leave a permanent dent. A 4leaves only a slight crease which is permanent but not as severe as 3. A5 represents virtually no visible indentation or damage of any sort.

[0174] The spin rate of the golf ball was measured by striking theresulting golf balls with a pitching wedge or 9 iron wherein the clubhead speed is about 105 feet per second and the ball is launched at anangle of 26 to 34 degrees with an initial velocity of about 110 to 115feet per second. The spin rate was measured by observing the rotation ofthe ball in flight using stop action Strobe photography.

[0175] Initial velocity is the velocity of a ball when struck at ahammer speed of 143.8 feet per second in accordance with a test asprescribed by the U.S.G.A.

[0176] As will be noted, compositions A, B and C include high acidionomeric resins, With composition B further including zinc stearate.Composition D represents the inner layer (i.e. Surlyn® 1605) used inU.S. Pat. No. 4,431,193. Composition E provides a hard, low acidionomeric resin.

[0177] The purpose behind producing and testing the balls of Table 16was to provide a subsequent comparison in properties with themulti-layer golf balls of the present invention. TABLE 16 MoldedIntermediate Golf Balls A B C D E Ingredients of Inner CoverCompositions Iotek ® 959 50 50 — — — Iotek ® 960 50 50 — — — ZincStearate — 50 — — — Surlyn ® 8162 — — 75 — — Surlyn ® 8422 — — 25 — —Surlyn ® 1605 — — — 100 — Iotek ® 7030 — — — — 50 Iotek ® 8000 — — — —50 Properties of Molded Intermediate Balls Compression 58 58 60 63 62C.O.R. .811 .810 .807 .793 .801 Shore C Hardness 98 98 97 96 96 SpinRate (R.P.M.) 7,367 6,250 7,903 8,337 7,956 Cut Resistance 4-5 4-5 4-54-5 4-5

[0178] As shown in Table 16 above, the high acid ionomer resin innercover layer (molded intermediate balls A-C) have lower spin rates andexhibit substantially higher resiliency characteristics than the lowacid ionomer resin based inner cover layers of balls D and E.

EXAMPLE 4

[0179] Multi-layer balls in accordance with the present invention werethen prepared. Specifically, the inner cover compositions used toproduce intermediate golf balls from Table 16 were molded over the solidcores to a thickness of about 0.0375 inches, thus forming the innerlayer. The diameter of the solid core with the inner layer measuredabout 1.620 inches. Alternatively, the intermediate golf balls of Table16 were ground down using a centerless grinding machine to a size of1.620 inches in diameter to produce an inner cover layer of 0.0375inches.

[0180] The size of 1.620 inches was determined after attempting to moldthe outer cover layer to various sizes (1.600″, 1.610″, 1.620″, 1.630″and 1.640″) of intermediate (core plus inner layer) balls. It wasdetermined that 1.620″ was about the largest “intermediate” ball (i.e.,core plus inner layer) which could be easily molded over with the softouter layer materials of choice. The goal herein was to use as thin anouter layer as necessary to achieve the desired playabilitycharacteristics while minimizing the cost of the more expensive outermaterials. However, with a larger diameter final golf ball and/or if thecover is compression molded, a thinner cover becomes feasible.

[0181] With the above in mind, an outer cover layer composition wasblended together in accordance with conventional blending techniques.The outer layer composition used for this portion of the example is arelatively soft cover composition such as those listed in U.S. Pat. No.5,120,791. An example of such a soft cover composition is a 45% soft/55%hard low acid ionomer blend designated by the inventor as “TE-90”. Thecomposition of TE-90 is set forth as follows: Outer Cover LayerComposition TE-90 Iotek ® 8000 22.7 weight % Iotek ® 7030 22.7 weight %Iotek ® 7520 45.0 weight % White MB¹  9.6 weight %

[0182] The above outer layer composition was molded around each of the1.620 diameter intermediate balls comprising a core plus one ofcompositions A-D, respectively. In addition, for comparison purposes,Surlyn® 1855 (new Surlyn® 9020), the cover composition of the '193patent, was molded about the inner layer of composition D (theintermediate ball representative of the '193 patent). The outer layerTE-90 was molded to a thickness of approximately 1.680 inches indiameter. The resulting balls (a dozen for each example) were tested andthe various properties thereof are set forth in Table 17 as follows:TABLE 17 Finished Balls Ingredients: 1 2 3 4 5 Inner Cover A B C D DComposition Outer Cover TE-90 TE-90 TE-90 TE-90 Surlyn ® 9020Composition Properties of Molded Finished Balls: Compression 63 63 69 7061 C.O.R. .784 .778 .780 .770 .757 Shore C Hardness 88 88 88 88 89 Spin(R.P.H.) 8,825 8,854 8,814 8,990 8,846 Cut Resistance 3-4 3-4 3-4 3-41-2

[0183] As it will be noted in finished balls 1-4, by creating amulti-layer cover utilizing the high acid ionomer resins in the innercover layer and the hard/soft low acid ionomer resin in the outer coverlayer, higher compression and increased spin rates are noted over thesingle layer covers of Table 16. In addition, both the C.O.R. and theShore C hardness are reduced over the respective single layer covers ofTable 16. This was once again particularly true with respect to themulti-layered balls containing the high acid ionomer resin in the innerlayer (i.e. finished balls 1-5). In addition, with the exception ofprior art ball 5 (i.e. the '193 patent), resistance to cutting remainsgood but is slightly decreased.

[0184] Furthermore, it is also noted that the use of the high acidionomer resins as the inner cover material produces a substantialincrease in the finished balls overall distance properties. In thisregard, the high acid ionomer resin inner covers of balls 1-3 produce anincrease of approximately 10 points in C.O.R. over the low acid ionomerresin inner covers of balls 4 and about a 25 point increase over theprior art balls 5. Since an increase in 3 to 6 points in C.O.R. resultsin an average increase of about 1 yard in distance, such an improvementis deemed to be significant.

[0185] Several other outer layer formulations were prepared and testedby molding them around the core and inner cover layer combination toform balls each having a diameter of about 1.68 inches. First, B.F.Goodrich Estane® X-4517 polyester polyurethane was molded about the coremolded with inner layer cover formulation A. DuPont Surlyn® 9020 wasmolded about the core which was already molded with inner layer D.Similar properties tests were conducted on these golf balls and theresults are set forth in Table 18 below: TABLE 18 Finished Balls 6 7Ingredients: Inner Cover Layer A D Composition Outer Cover LayerEstane ® 4517 Surlyn ® 9020 Composition Properties of Molded FinishedBalls: Compression 67 61 C.O.R. .774 .757 Shore C Hardness 74 89 Spin(R.P.M.) 10,061 8,846 Cut Resistance 3-4 1-2

[0186] The ball comprising inner layer formulation D and Surlyn® 9020identifies the ball in the Nesbitt U.S. Pat. No. 4,431,193. As is noted,the example provides for relatively high softness and spin rate thoughit suffers from poor cut resistance and low C.O.R. This ball isunacceptable by today's standards.

[0187] As for the Estane® X-4517 polyester polyurethane, a significantincrease in spin rate over the TE-90 cover is noted along with anincrease in spin rate over the TE-90 cover is noted along with anincreased compression. However, the C.O.R. and Shore C values arereduced, while the cut resistance remains the same. Furthermore, boththe Estane® X-4517 polyester polyurethane and the Surlyn® 9020 wererelatively difficult to mold in such thin sections.

EXAMPLE 5

[0188] In order to analyze the change in characteristics produced bymulti-layer golf balls (standard size) having inner cover layerscomprised of ionomer resin blends of different acid levels, a series ofexperiments was run. A number of tests were performed, varying the typeof core, inner cover layer and outer cover layer. The results are shownbelow on Table 19: TABLE 19 Inner Comp/ Outer COMP Sample # Core LayerThickness COR Cover Thickness (Rhiele) COR Shore D Spin 8 1042 None —See Below Top 0.055″ 61 .800 68 7331 Yellow Grade 9 1042 None — SeeBelow 959/960 0.055″ 56 .808 73 6516 Yellow 10 Special 959/960 0.050″65/.805 959/960 0.055″ 48 .830 73 6258 1.47″ 11 1042 None — See Below SD90 0.055″ 62 .792 653 8421 Yellow 12 Special Top 0.050″ 66/.799 SD 900.055″ 55 .811 63 8265 1.47″ Grade 13 Special 959/960 0.050″ 65/.805 SD90 0.055″ 53 .813 63 8254 1.47″ 14 Special Top 0.050″ 66/.799 Top 0.055″51 .819 68 7390 1.47″ Grade Grade 15 1042 None 0.050″ See Below Z-Balata0.055″ 67 .782 55 9479 Yellow 16 Special 959/960 0.050″ 65/.805 Z-Balata0.055″ 61 .800 55 9026 1.47″ 17 Special Top 0.050″ 66/.799 Z-Balata0.055″ 60 .798 55 9262 1.47″ Grade

[0189] In this regard, “Top Grade” or “TG” is a low acid inner coverionomer resin blend comprising of 70.6% lotek® 8000, 19.9% lotek® 7010and 9.6% white master batch. “959/960” is a 50/50 wttwt blend of lotek®959/960. In this regard, Escor® or lotek® 959 is a sodium ionneutralized ethylene-acrylic neutralized ethylene-acrylic acidcopolymer. According to Exxon, loteks® 959 and 960 contain from about19.0 to about 21.0% by weight acrylic acid with approximately 30 toabout 70 percent of the acid groups neutralized with sodium and zincions, respectively. The physical properties of these high acid acrylicacid based ionomers are as follows: TABLE 20 ESCOR ® ESCOR ® PROPERTY(IOTEK ®) 959 (IOTEK ®) 960 Melt Index g/10 min 2.0 1.8 Cation SodiumZinc Melting Point, ° F. 172 174 Vicat Softening Point, ° F. 130 131Tensile @ Break, psi 4600 3500 Elongation @ Break, % 325 430 Hardness,Shore D 66 57 Flexural Modulus, psi 66,000 27,000

[0190] Furthermore, the low acid ionomer formulations for “SD 90” and“Z-Balata” are set forth below: TABLE 21 SD Cover ZB Cover 17.2%Surlyn ® 8320   19% Iotek ® 8000  7.5% Surlyn ® 8120   19% Iotek ® 7030  49% Surlyn ® 9910 52.5% Iotek ® 7520 16.4% Surlyn ® 8940  9.5% whiteMB ®  9.7% white MB ®

[0191] The data clearly indicates that higher C.O.R. and hence increasetravel distance can be obtained by using multi-layered covered ballsversus balls covered with single layers. However, some sacrifices incompression and spin are also noted. Further, as shown in comparingExample Nos. 12 vs. 13, Example Nos. 17 vs. 16, etc. use of lower acidlevel inner cover layers and relatively soft outer cover layers (i.e.,50 wt. % or more soft ionomer) produces softer compression and higherspin rates than the golf balls comprised of high acid inner coverlayers. Consequently, use of blends of low acid ionomer resins toproduce the inner layer of a multi-layer covered golf ball, produces notonly enhanced travel distance but also enhanced compression and spinproperties.

EXAMPLE 6

[0192] Multi-layer oversized golf balls were produced utilizingdifferent ionomer resin blends as the inner cover layer (i.e., core plusinner cover layer is defined as “mantle”). The “ball data” of theoversized multi-layer golf balls in comparison with production samplesof “Top-Flite® XL” and Top-Flite® Z-Balata” is set forth below.

[0193] The results indicate that use of multi-layer covers enhancesC.O.R. and travel distance. Further, the data shows that use of a blendof low acid ionomer resins (i.e., “Top Grade”) to form the inner coverlayer in combination with a soft outer cover (“ZB” or “SD”) producesenhanced spin and compression characteristics. The overall combinationresults in a relatively optimal golf ball with respect tocharacteristics of travel distance, spin and durability.

EXAMPLE 7

[0194] Golf balls 7-1, 7-2, 7-3 and 7-4 having the formulations shown onTable 22 were formed. TABLE 22 Chemical Component 7-1 7-2 7-3 7-4 CoreData Size 1.47″ 1.47″ 1.47″ 1.47″ Weight 32.7 g 32.7 g 32.7 g 32.7 g PGACompression 70 60 70 60 COR .780 .770 .780 .770 Composition High Cispolybutadiene 100 100 100 100 Zinc oxide 30.5 31.6 30.5 31.6 Coreregrind 16 16 16 16 Zinc stearate 16 16 16 16 Zinc diacrylate 22 20 2220 Initiator 0.9 0.9 0.9 0.9 Inner Cover Layer Size 1.57″ 1.57″ 1.57″1.57″ Weight 38.04 g 38.4 g 38.4 g 38.4 g PGA Compression 83 75 83 75COR .801 .795 .801 .795 Thickness 0.050″ 0.050″ 0.050″ 0.050″ Hardness(Shore C/D) 97/70 97/70 97/70 97/70 Composition Iotek ® 1002 50% 50% 50%50% Iotek ® 1003 50% 50% 50% 50% Outer Cover Layer Hardness (Shore C/D)71/46 71/46 71/46 71/46 Thickness 0.055″ 0.055″ 0.055″ 0.055″Composition Iotek ® 7510 92.8% 92.8% 42% 42% Iotek ® 7520 42% 42%Iotek ® 7030 7.2% 7.2% 7.3% 7.3% Iotek ® 8000 8.7% 8.7% Whitener PackageUnitane ™ 0-110 2.3 phr 2.3 phr 2.3 phr 2.3 phr Eastobrite ® OB1 0.025phr 0.025 phr 0.025 phr 0.025 phr Ultra Marine Blue ™ 0.042 phr 0.042phr 0.042 phr 0.042 phr Santonox ® 0.004 phr 0.004 phr 0.004 phr 0.004phr Final Ball Data Size 1.68″ 1.68″ 1.68″ 1.68″ Weight 45.4 g 45.4 g45.4 g 45.4 g PGA Compression 85 78 85 78 COR .793 .785 .793 .785

[0195] The balls of Example 7-2 were tested by a number of professionalquality golfers using a driver, 5-iron, 9-iron, and sand wedge orpitching wedge. Each player used his own clubs and hit both the ball ofExample 7-2 and a control ball, which was the 1995 two-piece Top-Flite®Tour Z-balata 90. The Z-balata 90 has a 1.545″ core of about 36.8 g witha PGA compression of about 80 and a COR of about 0.794. The cover of theZ-balata 90 is about 0.068 in. thick, and is a blend of lotek® 8000 andlotek® 7510 with or without master batch containing lotek® 7030. Thecover has a shore D hardness of about 55. The ball has a PGA compressionof about 79 and a COR of about 0.788. Each player hit six of the ballsof Example 7-2 and six Z-balata control balls one time each. For eachshot, measurements were made of the initial launch conditions of thegolf ball, including launch angle and ball speed. Furthermore, spinrates at initial launch, carry distance, and total distance weremeasured. The players hit full shots with the driver (1W), 5-iron (5I)and 9-iron (9I). With the sand wedge or pitching wedge (SW), the playershit about 30 yard chip shots. Data points were removed if determined tobe “wild points.” A point was said to be wild if it fell outside 2standard deviations of the 6-hit average. Initial launch conditions weredetermined using a highly accurate high speed stop action videophotography system. The results are shown on Table 23.

[0196] As shown on Table 23, multi-layer ball 7-2 was longer than theZ-balata control when hit with a 5-iron but only slightly longer thanthe Z-balata ball using a driver and 9-iron. The multi-layer ball 7-2and the two-piece control were generally the same in overall distanceusing a driver. In each case, the multi-layer ball 7-2 had a higher spinrate off the 30-yard chip shot than the Z-balata. The spin rate of theball of Example 7-2 was an average of 11.6% higher than the spin rate ofthe Z-balata control in the 30 yard chip shot. TABLE 23 2-Piece Control7-2 L.A. B.S. Spin Carry Total L.A. B.S. Spin Carry Total Player Club(deg) (fps) (rpm) (yds) (yds) (deg) (fps) (rpm) (yds) (yds) 1 1W 10.4262.2 3537 272.5 288.9 10.0 262.3 3247 271.6 292.2  2 1W 9.5 240.1 3124238.1 253.6 8.9 238.3 2935 236.3 257.4  3 1W 8.6 258.8 3695 254.1 259.96.3 251.2 3357 247.6 260.8  4 1W 10.9 252.6 2639 271.6 289.8 12.5 251.43066 279.0 296.7  5 1W 9.5 211.7 3627 237.2 255.2 9.4 208.7 3415 235.0259.8  6 1W 10.2 242.0 3105 263.8 283.2 11.0 243.9 2903 267.6 288.4  71W 11.5 214.9 3089 265.4 279.0 11.6 212.6 3165 262.9 274.4  8 1W 9.7239.5 3129 263.6 28.8 9.3 235.3 2884 257.2 276.8  9 1W 11.7 211.2 2939231.4 255.8 11.3 208.5 2032 222.2 244.3 10 1W 10.2 244.0 2797 243.3250.2 9.7 239.6 3072 236.8 251.1 11 1W 247.4 263.8 13.8 215.8 3916 245.4268.8 Ave. 10.2 237.7 3168 253.5 269.8 10.3 233.4 3090 251.1 270.1  1 5I12.4 207.3 5942 198.3 209.8 11.8 206.3 5507 196.2 207.8  2 5I 178.3184.2 14.9 199.4 5094 182.2 187.8  3 5I 10.9 196.8 6462 185.2 188.9 11.5197.0 6009 187.4 193.4  4 5I 14.4 205.5 6683 207.8 213.7 14.7 208.3 6601207.5 217.8  5 5I 13.6 183.3 6734 182.9 189.4 14.2 180.9 6380 184.2190.7  6 5I 12.4 204.5 5771 201.0 210.5 12.9 208.4 5414 208.0 218.3  75I 14.1 184.3 6013 194.8 198.1 13.1 182.7 6000 192.9 200.0  8 5I 12.8187.2 6149 188.0 200.3 13.1 191.6 6183 191.7 202.0  9 5I 13.2 176.5 6000168.2 173.7 13.6 172.5 6166 169.7 174.3 10 5I 13.9 199.9 7214 175.2178.2 14.9 199.1 6237 169.0 170.2 11 5I 14.2 179.5 6669 181.9 187.8 15.7181.2 5338 184.0 190.7 Ave. 13.2 192.5 6364 187.4 194.1 13.7 193.4 5903188.4 195.7  1 9I 20.0 168.1 9865 152.5 159.5 20.4 172.2 9210 153.4159.6  2 9I 21.8 165.9 9770 132.7 137.0 23.0 164.7 8949 132.7 134.6  39I 19.9 154.3 10764 128.8 134.3 19.9 156.5 1061 129.8 135.0  4 9I 22.7166.4 10551 146.0 148.8 23.9 165.7 9990 150.3 154.2  5 9I 22.1 147.49682 137.1 138.1 22.2 148.5 9324 139.3 141.7  6 9I 19.4 169.7 8939 153.3158.0 19.7 168.2 8588 156.2 163.5  7 9I 20.4 151.1 9899 147.5 150.0 21.6150.3 9084 148.6 151.3  8 9I 18.5 143.0 9408 142.0 147.5 18.3 141.8 9038141.2 144.8  9 9I 20.0 134.5 9124 124.9 128.8 20.1 132.9 8834 125.0128.9 10 9I 23.2 156.1 10603 122.7 124.1 23.2 155.6 11017 116.2 116.3 119I 21.5 149.4 9729 131.0 134.5 23.4 151.7 8686 133.3 136.8 Ave. 20.9155.1 9849 138.0 141.9 21.4 155.3 9353 138.7 142.4  1 SW 29.2 56.4 564724.8 58.9 6679  2 SW 26.6 57.4 5446 25.2 57.8 5647  3 SW 25.8 64.1 492524.3 63.5 5550  4 SW 30.9 60.9 5837 31.1 57.9 6158  5 SW 20.3 56.7 415219.0 56.3 4288  6 SW 34.3 57.1 3798 32.4 61.5 4700  7 SW 30.5 51.5 471229.3 52.3 5374 Ave. 28.2 67.7 4931 26.6 58.3 6485

EXAMPLE 8

[0197] The ball of Example 7-2 was compared to a number of competitiveproducts in distance testing using a driving machine in which the ballwas struck with a club. The results are shown on Table 24 below. Thedistance test shows that Example 7-2 about the same distance as theZ-balata 90 control and longer than the Titleist® HP-2 Tour (softcovered two-piece) and Titleist® Tour Balata 100 ball (Balata coveredwound ball). The other balls that were tested include the Maxfli®(Dunlop) XS1 00, Maxfli® (Dunlop) XF1 00, and the GIGA Top-Flite® golfball sold by in Japan. In Table 24, the ball of Example 7-2 is thelongest ball. TABLE 24 Distance Report Test Number: 131951 Club HeadSpeed: 157.35 Club Name: TFT 10.5 DEG MW No. Balls/Type: 10 (Driver)Average Test Conditions: Launch Angels (Deg.): 9.6 Ball Speed (fps):217.9 Spin Rate (rpm): 3390 Turf Condition: FIRM Wind (mph/dir): 2.55135.20 Temp/RH (deg/%): 0.61 91.59 P-Bar (mbar): 1015 Car Ctr T T BallType Traj PTime Carry Diff Dev Roll Dist Diff HP2TOUR 8.7 6.0 230.4 −4.13.0 9.9 240.3 −4.3 ZB90 9.0 6.1 231.8 −2.7 5.4 9.1 241.0 −3.6 GIGA 8.86.0 234.5 0.0 5.7 10.2 244.6 0.0 Example 7-2 8.3 5.9 229.6 −4.9 3.8 11.1240.7 −3.9 Titleist Tour 9.2 6.2 229.2 −5.3 7.8 7.8 236.9 −7.7 Balata100 Test Number: 0203963 Club Head Speed: 126.18 Club Name: TFT 5 IRONNo. Balls/Type: 12 Average Test Conditions: Launch Angels (Deg.): 14Ball Speed (fps): 180.1 Spin Rate (rpm): 5424 Turf Condition: FIRM Wind(mph/dir): 6.23 171.38 Temp/RH (deg/%): 62.20 98.16 P-Bar (mbar): 1015Car Ctr T T Ball Type Traj PTime Carry Diff Dev Roll Dist Diff HP2TOUR25.3 6.0 156.0 −7.4 −3.0 1.5 157.5 −9.5 ZB90 25.2 6.0 157.1 −6.3 −3.32.2 159.3 −7.7 GIGA 25.0 6.0 162.2 −1.2 −3.1 2.9 165.1 −1.9 Example 7-223.5 6.0 163.4 0.0 −3.3 3.7 167.0 0.0 Titleist Tour 23.9 6.0 158.7 −4.7−2.3 2.5 161.2 −5.8 Balata 100 ZB 100 26.1 6.0 155.6 −7.8 −4.5 2.0 157.6−9.4 XS 100 23.9 6.0 161.3 −2.3 −5.6 2.6 163.9 −3.1 XF 100 24.5 6.0152.0 −11.4 −6.2 1.6 153.7 −13.3

EXAMPLE 9

[0198] A number of golf ball cores having the following formulation weremade:

[0199] Parts High-cis polybutadiene 100 Zinc oxide 30 Core regrind 16Zinc stearate 16 Zinc diacrylate 21 Peroxide (231 xl) 0.9

[0200] The cores had a diameter of 1.470″, a weight of 32.5 g, a PGAcompression of 57 and a COR of 0.768.

[0201] The cores were divided into four sets and each set was coveredwith one of the mantle formulations shown below in Table 25. TABLE 25MANTLE FORMULATIONS Mantle Type A B C D (control) Surlyn ® 8940 (g) 656880 1610 — Surlyn ® 9910 (g) 1964 2180 535 — Surlyn ® 8120 (g) 300 160475 — Surlyn ® 8320 (g) 700 400 1000 — Iotek ® 7030 (g) 380 380 380 —Iotek ® 1002 (g) — — — 2000 Iotek ® 1003 (g) — — — 2000

[0202] The mantle covered cores had the following physical properties:TABLE 26 MANTLE-COVERED CORES A B C D Size (Pole) (Inches) 1.577 1.5761.572 1.573 Weight (g) 38.6 38.5 38.3 38.4 PGA Compression 71 74 70 76COR .7795 .7831 .7768 .7946 Std. Dev. COR .0051 .0026 .0016 .0012 ShoreC 92 94 90 97 Shore D 62 65 61 70

[0203] Each set of mantle-covered cores was divided into three subsetsand a cover layer having one of the cover formulations shown below onTable 27 was formed over the mantled cores. The “whitener package” onTable 27 consists of White MB, the composition of which was previouslydescribed herein. TABLE 27 COVER FORMULATIONS Cover Type X Y Z Iotek ®7520 (g) 1660 1480 1300 Iotek ® 7510 (g) 1660 1480 1300 Iotek ® 8000 (g)304 664 1024 Iotek ® 7030 (g) 282 282 282 Whitener package (g) 94 94 94

[0204] The balls had the mantle and cover combinations and propertiesshown below on Table 28. TABLE 28 Ball Properties Example No. 9-1 9-29-3 9-4 9-5 9-6 9-7 9-8 9-9 9-10 9-11 9-12 Mantle A A A B B B C C C D DD Cover X Y Z X Y Z X Y Z X Y Z Size 1.682 1.681 1.682 1.682 16.82 1.6821.682 1.682 1.681 1.682 1.682 1.681 (inch) Weight 45.68 45.57 45.5845.77 45.62 45.58 45.63 45.58 45.48 45.67 45.65 45.57 (g) PGA 73.5 74.374.7 77.4 76.7 76.3 70.8 71.9 73.3 79.5 80 82.5 Comp. COR .7639 .7665.7680 .7701 .7703 .7704 .7607 .7630 .7661 .7771 .7798 .7839 Std. .0041.0027 .0037 .0077 .0034 .0023 .0037 .0030 .0028 .0034 .0028 .0020 Dev.COR Shore C 71 76 81 71 76 81 70 76 80 71 76 81 Shore D 48 50 53 46 5053 46 49 52 47 41 53

[0205] Ball 9-10 was the control.

[0206] The results from Table 28 demonstrate that a multi-layer ballhaving a mantle hardness of 60 D or greater (Ex. 9-7,9-8, 9-9), andpreferably 63 D (Ex. 9-1, 9-2, 9-3) or greater give a ball having a CORof at least 0.761 (Ex. 9-7) and while a harder mantle (Ex. (9-4, 9-5,9-6, 9-10, 9-11, 9-12) will generally give higher COR, it alsocontributes to a harder PGA compression. Versus the control ball (Ex.9-10) it is demonstrated that softer compressions can be obtained withslightly softer mantles while maintaining a good COR. Likewise versusthe control, higher COR balls may be designed (Ex. 9-11, 9-12) thatstill have a relatively soft compression for good feel.

EXAMPLE 10

[0207] A number of golf balls were made having the core and coverformulations and the physical properties shown on Tables 29 and 30. Theballs of Examples 10-1, 10-2 and 10-5 are part of the invention. Theballs of Examples 10-3, 10-4 and 10-6 are controls based upon the coverlayer chemistry of comparative Example 2 of U.S. Pat. No. 5,586,950. Theballs of Example 10-4 are replicas of comparative Example 2 of U.S. Pat.No. 5,586,950.

[0208] For all of the balls, the cores were molded and centerless groundto the appropriate size. The mantles of Examples 10-1 to 10-4 wereinjection molded in a 1.63″ injection mold. The mantles for the balls ofExamples 10-5 and 10-6 also were injection molded. All of the outercover layers were injection molded. TABLE 29 Core Data Ex. 10-1 Ex. 10-2Ex. 10-3 Ex. 10-4 Ex. 10-5 Ex. 10-6 Core Types (See Table 2) A A A A B BMantle Data 1.50 1.50 1.50 1.50 1.47 1.47 Ingredients phr phr phr phrphr phr Iotek ® 1002 50 — 50 — 50 50 Iotek ® 1003 50 — 50 — 50 50Surlyn ® 9910 — 50 — 50 — — Surlyn ® 8940 — 35 — 35 — — Surlyn ® 8920 —15 — 15 — — TiO₂ 2 2 2 2 — — Diameter (in.) 1.625 1.625 1.625 1.625 1.571.57 Thickness (in.) 0.063 0.063 0.063 0.063 0.050 0.050 Shore C/DHardness 97/70 96/68 97/70 96/68 97/70 97/70 (measured on ball) CoverData Cover Type (see Table 2) #1 #1 #2 #2 #1 #2 Size (in.) 1.70 1.701.70 1.70 1.68 1.68 Thickness (in.) 0.038 0.038 0.038 0.038 0.055 0.055Shore C/D Hardness 75/49 75/49 84/57 83/57 72/48 83/56 (measured onball) Compression (Rhiele) 63 66 60 63 83 80 COR .800 .795 .805 .798.779 .787

[0209] TABLE 30 Core Formulations Cover Formulations Materials (phr) A BMaterials (phr) #1 #2 BR 1220 (High cis 73 70 Iotek ® 8000 8.5 —polybutadiene) Taktene ® 220 (High cis 27 30 Iotek ® 7510 41 —polybutadiene) Zinc Oxide 22.3 31.5 Iotek ® 7520 41 — TG Regrind 10 16Master batch C 9.5 — Zinc Stearate 20 16 Surlyn ® 1557 — 10 ZincDiacrylate 26 20 Surlyn ® 1855 — 20 Master batch A 0.15 — Surlyn ® 8265— 20 Master batch B — 0.15 Surlyn ® 8269 — 50 Luperco ® 231 XL peroxide0.9 0.9 TiO2 — 2

[0210] Definitions

[0211] Coefficient of Restitution

[0212] As is apparent from the above discussions, two principalproperties involved in golf ball performance are resilience and PGAcompression. The resilience or coefficient of restitution (COR) of agolf ball is the constant “e,” which is the ratio of the relativevelocity of an elastic sphere after direct impact to that before impact.As a result, the COR (“e”) can vary from 0 to 1, with 1 being equivalentto a perfectly or completely elastic collision and 0 being equivalent toa perfectly or completely inelastic collision.

[0213] COR, along with additional factors such as club head speed, clubhead mass, ball weight, ball size and density, spin rate, angle oftrajectory and surface configuration (i.e., dimple pattern and area ofdimple coverage) as well as environmental conditions (e.g. temperature,moisture, atmospheric pressure, wind, etc.) generally determine thedistance a ball will travel when hit. Along this line, the distance agolf ball will travel under controlled environmental conditions is afunction of the speed and mass of the club and size, density andresilience (COR) of the ball and other factors. The initial velocity ofthe club, the mass of the club and the angle of the ball's departure areessentially provided by the golfer upon striking. Since club head, clubhead mass, the angle of trajectory and environmental conditions are notdeterminants controllable by golf ball producers and the ball size andweight are set by the U.S.G.A., these are not factors of concern amonggolf ball manufacturers. The factors or determinants of interest withrespect to improved distance are generally the coefficient ofrestitution (COR) and the surface configuration (dimple pattern, ratioof land area to dimple area, etc.) of the ball.

[0214] The COR of solid core balls is a function of the composition ofthe core and of the cover. The core and/or cover may be comprised of oneor more layers such as in multi-layered balls. In balls containing awound core (i.e., balls comprising a liquid or solid center, elasticwindings, and a cover), the coefficient of restitution is a function ofnot only the composition of the center and cover, but also thecomposition and tension of the elastomeric windings. As in the solidcore balls, the center and cover of a wound core ball may also consistof one or more layers. The COR of the golf balls of the presentinvention is a function of the composition and physical properties ofthe core and cover layer materials such as flex modulus, hardness andparticularly, their resilience, i.e. ability to quickly recover from ahigh impact deformation.

[0215] The coefficient of restitution is the ratio of the outgoingvelocity to the incoming velocity. In the examples of this application,the coefficient of restitution of a golf ball was measured by propellinga ball horizontally at a speed of 125±5 feet per second (fps) andcorrected to 125 fps against a generally vertical, hard, flat steelplate and measuring the ball's incoming and outgoing velocityelectronically. Speeds were measured with a pair of Oehler Mark 55ballistic screens available from Oehler Research, Inc., P.O. Box 9135,Austin, Tex. 78766, which provide a timing pulse when an object passesthrough them. The screens were separated by 36″ and are located 25.25″and 61.25″ from the rebound wall. The ball speed was measured by timingthe pulses from screen 1 to screen 2 on the way into the rebound wall(as the average speed of the ball over 36″), and then the exit speed wastimed from screen 2 to screen 1 over the same distance. The rebound wallwas tilted 2 degrees from a vertical plane to allow the ball to reboundslightly downward in order to miss the edge of the cannon that fired it.The rebound wall is solid steel 2.0 inches thick.

[0216] As indicated above, the incoming speed should be 125±5 fps butcorrected to 125 fps. The correlation between COR and forward orincoming speed has been studied and a correction has been made over the±5 fps range so that the COR is reported as if the ball had an incomingspeed of exactly 125.0 fps.

[0217] The coefficient of restitution must be carefully controlled inall commercial golf balls if the ball is to be within the specificationsregulated by the United States Golf Association (U.S.G.A.). As mentionedto some degree above, the U.S.G.A. standards indicate that a“regulation” ball cannot have an initial velocity exceeding 255 feet persecond in an atmosphere of 75° F. when tested on a U.S.G.A. machine.Since the coefficient of restitution of a ball is related to the ball'sinitial velocity, it is highly desirable to produce a ball havingsufficiently high coefficient of restitution to closely approach theU.S.G.A. limit on initial velocity, while having an ample degree ofsoftness (i.e., hardness) to produce enhanced playability (i.e., spin,etc.).

[0218] PGA Compression

[0219] PGA compression is another important property involved in theperformance of a golf ball. The compression of the ball can affect theplayability of the ball on striking and the sound or “click” produced.Similarly, compression can affect the “feel” of the ball (i.e., hard orsoft responsive feel), particularly in chipping and putting.

[0220] Moreover, while compression itself has little bearing on thedistance performance of a ball, compression can affect the playabilityof the ball on striking. The degree of compression of a ball against theclub face and the softness of the cover strongly influences theresultant spin rate. Typically, a softer cover will produce a higherspin rate than a harder cover. Additionally, a harder core will producea higher spin rate than a softer core. This is because at impact a hardcore serves to compress the cover of the ball against the face of theclub to a much greater degree than a soft core thereby resulting in more“grab” of the ball on the clubface and subsequent higher spin rates. Ineffect the cover is squeezed between the relatively incompressible coreand clubhead. When a softer core is used, the cover is under much lesscompressive stress than when a harder core is used and therefore doesnot contact the clubface as intimately. This results in lower spinrates. The term “compression” utilized in the golf ball trade generallydefines the overall deflection that a golf ball undergoes when subjectedto a compressive load. For example, PGA compression indicates the amountof change in golf ball's shape upon striking.

[0221] In the past, PGA compression related to a scale of from 0 to 200given to a golf ball. The lower the PGA compression value, the softerthe feel of the ball upon striking. In practice, tournament qualityballs have compression ratings around 70-110, preferably around 80 to100.

[0222] In determining PGA compression using the 0-200 scale, a standardforce is applied to the external surface of the ball. A ball whichexhibits no deflection (0.0 inches in deflection) is rated 200 and aball which deflects {fraction (2/10)}th of an inch (0.2 inches) is rated0. Every change of 0.001 of an inch in deflection represents a 1 pointdrop in compression. Consequently, a ball which deflects 0.1 inches(100×0.001 inches) has a PGA compression value of 100 (i.e., 200-100)and a ball which deflects 0.110 inches (110×0.001 inches) has a PGAcompression of 90 (i.e., 200-110).

[0223] In order to assist in the determination of compression, severaldevices have been employed by the industry. For example, PGA compressionis determined by an apparatus fashioned in the form of a small presswith an upper and lower anvil. The upper anvil is at rest against a200-pound die spring, and the lower anvil is movable through 0.300inches by means of a crank mechanism. In its open position the gapbetween the anvils is 1.780 inches allowing a clearance of 0.100 inchesfor insertion of the ball. As the lower anvil is raised by the crank, itcompresses the ball against the upper anvil, such compression occurringduring the last 0.200 inches of stroke of the lower anvil, the ball thenloading the upper anvil which in turn loads the spring. The equilibriumpoint of the upper anvil is measured by a dial micrometer if the anvilis deflected by the ball more than 0.100 inches (less deflection issimply regarded as zero compression) and the reading on the micrometerdial is referred to as the compression of the ball. In practice,tournament quality balls have compression ratings around 80 to 100 whichmeans that the upper anvil was deflected a total of 0.120 to 0.100inches.

[0224] An example to determine PGA compression can be shown by utilizinga golf ball compression tester produced by Atti Engineering Corporationof Newark, N.J. The value obtained by this tester relates to anarbitrary value expressed by a number which may range from 0 to 100,although a value of 200 can be measured as indicated by two revolutionsof the dial indicator on the apparatus. The value obtained defines thedeflection that a golf ball undergoes when subjected to compressiveloading. The Atti test apparatus consists of a lower movable platformand an upper movable spring-loaded anvil. The dial indicator is mountedsuch that it measures the upward movement of the springloaded anvil. Thegolf ball to be tested is placed in the lower platform, which is thenraised a fixed distance. The upper portion of the golf ball comes incontact with and exerts a pressure on the springloaded anvil. Dependingupon the distance of the golf ball to be compressed, the upper anvil isforced upward against the spring.

[0225] Alternative devices have also been employed to determinecompression. For example, Applicant also utilizes a modified RiehleCompression Machine originally produced by Riehle Bros. Testing MachineCompany, Phil., PA to evaluate compression of the various components(i.e., cores, mantle cover balls, finished balls, etc.) of the golfballs. The Riehle compression device determines deformation inthousandths of an inch under a load designed to emulate the 200 poundspring constant of the Atti or PGA compression testers. Using such adevice, a Riehle compression of 61 corresponds to a deflection underload of 0.061 inches.

[0226] Additionally, an approximate relationship between Riehlecompression and PGA compression exists for balls of the same size. Ithas been determined by Applicant that Riehle compression corresponds toPGA compression by the general formula PGA compression=160−Riehlecompression. Consequently, 80 Riehle compression corresponds to 80 PGAcompression, 70 Riehle compression corresponds to 90 PGA compression,and 60 Riehle compression corresponds to 100 PGA compression. Forreporting purposes, Applicant's compression values are usually measuredas Riehle compression and converted to PGA compression.

[0227] Furthermore, additional compression devices may also be utilizedto monitor golf ball compression so long as the correlation to PGAcompression is know. These devices have been designed, such as a WhitneyTester, to correlate or correspond to PGA compression through a setrelationship or formula.

[0228] Shore D Hardness

[0229] As used herein, “Shore D hardness” of a cover is measuredgenerally in accordance with ASTM D-2240, except the measurements aremade on the curved surface of a molded cover, rather than on a plaque.Furthermore, the Shore D hardness of the cover is measured while thecover remains over the core. When a hardness measurement is made on adimpled cover, Shore D hardness is measured at a land area of thedimpled cover.

[0230] Fillers

[0231] In a particularly preferred form of the invention, at least onelayer of the golf ball contains at least 0.01 parts by weight of afiller. Fillers preferably are used to adjust the density, flex modulus,mold release, and/or melt flow index of a layer. More preferably, atleast when the filler is for adjustment of density or flex modulus of alayer, it is present in an amount of at least five parts by weight basedupon 100 parts by weight of the layer composition. With some fillers, upto about 200 parts by weight probably can be used.

[0232] A density adjusting filler according to the invention preferablyis a filler which has a specific gravity which is at least 0.05 and morepreferably at least 0.1 higher or lower than the specific gravity of thelayer composition. Particularly preferred density adjusting fillers havespecific gravities which are higher than the specific gravity of theresin composition by 0.2 or more, even more preferably by 2.0 or more.

[0233] A flex modulus adjusting filler according to the invention is afiller which, when used in an amount of e.g. 1-100 parts by weight basedupon 100 parts by weight of resin composition, will raise or lower theflex modulus (ASTM D-790) of the resin composition by at least 1% andpreferably at least 5% as compared to the flex modulus of the resincomposition without the inclusion of the flex modulus adjusting filler.

[0234] A mold release adjusting filler is a filler which allows for theeasier removal of a part from a mold, and eliminates or reduces the needfor external release agents which otherwise could be applied to themold. A mold release adjusting filler typically is used in an amount ofup to about 2 wt % based upon the total weight of the layer.

[0235] A melt flow index adjusting filler is a filler which increases ordecreases the melt flow, or ease of processing of the composition.

[0236] The layers may contain coupling agents that increase adhesion ofmaterials within a particular layer e.g. to couple a filler to a resincomposition, or between adjacent layers. Non-limiting examples ofcoupling agents include titanates, zirconates and silanes. Couplingagents typically are used in amounts of 0.1-2 wt % based upon the totalweight of the composition in which the coupling agent is included.

[0237] A density adjusting filler is used to control the moment ofinertia, and thus the initial spin rate of the ball and spin decay. Theaddition in one or more layers, and particularly in the outer coverlayer of a filler with a lower specific gravity than the resincomposition results in a decrease in moment of inertia and a higherinitial spin rate than would result if no filler were used. The additionin one or more of the cover layers, and particularly in the outer coverlayer of a filler with a higher specific gravity than the resincomposition, results in an increase in moment of inertia and a lowerinitial spin rate. High specific gravity fillers are preferred as lessvolume is used to achieve the desired inner cover total weight.Nonreinforcing fillers are also preferred as they have minimal effect onCOR. Preferably, the filler does not chemically react with the resincomposition to a substantial degree, although some reaction may occurwhen, for example, zinc oxide is used in a shell layer which containssome ionomer.

[0238] The density-increasing fillers for use in the inventionpreferably have a specific gravity in the range of 1.0-20. Thedensity-reducing fillers for use in the invention preferably have aspecific gravity of 0.06-1.4, and more preferably 0.06-0.90. The flexmodulus increasing fillers have a reinforcing or stiffening effect dueto their morphology, their interaction with the resin, or their inherentphysical properties. The flex modulus reducing fillers have an oppositeeffect due to their relatively flexible properties compared to thematrix resin. The melt flow index increasing fillers have a flowenhancing effect due to their relatively high melt flow versus thematrix. The melt flow index decreasing fillers have an opposite effectdue to their relatively low melt flow index versus the matrix.

[0239] Fillers which may be employed in layers other than the outercover layer may be or are typically in a finely divided form, forexample, in a size generally less than about 20 mesh, preferably lessthan about 100 mesh U.S. standard size, except for fibers and flock,which are generally elongated. Flock and fiber sizes should be smallenough to facilitate processing. Filler particle size will depend upondesired effect, cost, ease of addition, and dusting considerations. Thefiller preferably is selected from the group consisting of precipitatedhydrated silica, clay, talc, asbestos, glass fibers, aramid fibers,mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone,silicates, silicon carbide, diatomaceous earth, polyvinyl chloride,carbonates, metals, metal alloys, tungsten carbide, metal oxides, metalstearates, particulate carbonaceous materials, micro balloons, andcombinations thereof. Non-limiting examples of suitable fillers, theirdensities, and their preferred uses are as follows: TABLE 31 Filler TypeSpec. Grav. Comments Precipitated hydrated silica 2.0 1,2 Clay 2.62 1,2Talc 2.85 1,2 Asbestos 2.5 1,2 Glass fibers 2.55 1,2 Aramid fibers(KEVLAR ®) 1.44 1,2 Mica 2.8 1,2 Calcium metasilicate 2.9 1,2 Bariumsulfate 4.6 1,2 Zinc sulfide 4.1 1,2 Lithopone 4.2-4.3 1,2 Silicates 2.11,2 Silicon carbide platelets 3.18 1,2 Silicon carbide whiskers 3.2 1,2Tungsten carbide 15.6 1 Diatomaceous earth 2.3 1,2 Polyvinyl chloride1.41 1,2 Carbonates Calcium carbonate 2.71 1,2 Magnesium carbonate 2.201,2 Metals and Alloys (powders) Titanium 4.51 1 Tungsten 19.35 1Aluminum 2.70 1 Bismuth 9.78 1 Nickel 8.90 1 Molybdenum 10.2 1 Iron 7.861 Steel 7.8-7.9 1 Lead 11.4 1,2 Copper 8.94 1 Brass 8.2-8.4 1 Boron 2.341 Boron carbide whiskers 2.52 1,2 Bronze 8.70-8.74 1 Cobalt 8.92 1Beryllium 1.84 1 Zinc 7.14 1 Tin 7.31 1 Metal Oxides Zinc oxide 5.57 1,2Iron oxide 5.1 1,2 Aluminum oxide 4.0 Titanium oxide 3.9-4.1 1,2Magnesium oxide 3.3-3.5 1,2 Zirconium oxide 5.73 1,2 Metal StearatesZinc stearate 1.09 3,4 Calcium stearate 1.03 3,4 Barium stearate 1.233,4 Lithium stearate 1.01 3,4 Magnesium stearate 1.03 3,4 Particulatecarbonaceous materials Graphite 1.5-1.8 1,2 Carbon black 1.8 1,2 Naturalbitumen 1.2-1.4 1,2 Cotton flock 1.3-1.4 1,2 Cellulose flock 1.15-1.5 1,2 Leather fiber 1.2-1.4 1,2 Micro balloons Glass 0.15-1.1  1,2 Ceramic0.2-0.7 1,2 Fly ash 0.6-0.8 1,2 Coupling Agents Adhesion PromotersTitanates 0.95-1.17 Zirconates 0.92-1.11 Silane 0.95-1.2 

[0240] All fillers except for metal stearates would be expected toreduce the melt flow index of the cover layer.

[0241] The amount of filler employed is primarily a function of weightrequirements and distribution.

[0242] The invention has been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon reading and understanding the proceeding detaileddescription. It is intended that the invention be construed as includingall such modifications and alterations insofar as they come within thescope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A golf ball comprising: a core; a thermoplasticinner cover layer disposed about the core, the inner cover layer havinga Shore D hardness of at least 60 as measured on the curved surfacethereof; and an outer cover layer disposed on the inner cover layer, theouter cover layer having a Shore D hardness of no more than 55 asmeasured on the curved surface thereof; wherein the golf ball exhibits aPGA compression of 100 or less and a coefficient of restitution of atleast 0.770.
 2. The golf ball according to claim 1, wherein the innercover layer comprises a composition including at least one materialselected from the group consisting of polyphenylene ether/ionomerblends, ionomers, polyamides, polyurethanes, polyester elastomers,polyester amides, metallocene catalyzed polyolefins, and blends thereof.3. The golf ball according to claim 2, wherein the inner cover layercomprises ionomer.
 4. The golf ball according to claim 1, wherein theouter cover layer comprises a composition including at least onematerial selected from the group consisting of polyphenyleneether/ionomer blends, ionomers, polyamides, polyurethanes, polyesterelastomers, polyester amides, metallocene catalyzed polyolefins, andblends thereof.
 5. The golf ball according to claim 4, wherein the outercover layer comprises a composition including at least one materialselected from the group consisting of ionomers, polyurethanes, andblends thereof.
 6. The golf ball according to claim 5, wherein the outercover layer comprises polyurethane.
 7. The golf ball according to claim4, wherein the outer cover layer has a flex modulus of from about 1,000to about 10,000 psi.
 8. The golf ball according to claim 7, wherein theouter cover layer has a Shore D hardness of from about 30 to about 53.9. The golf ball according to claim 1, wherein the golf ball exhibits acoefficient of restitution of at least 0.780.
 10. A golf ballcomprising: a core; an inner cover layer disposed on the core, the innercover layer having a Shore D hardness of at least 60 as measured on thecurved outer surface thereof, and including at least one materialselected from the group consisting of polyphenylene ether/ionomerblends, ionomers, polyamides, polyurethanes, polyester elastomers,polyester amides, metallocene catalyzed polyolefins, and blends thereof;and an outer cover layer disposed about the inner cover layer, the outercover layer having a Shore D hardness of no more than 55 as measured onthe curved surface thereof; wherein the golf ball having a spin factorof at least about 5, a PGA compression of 100 or less, and a coefficientof restitution of at least 0.770.
 11. The golf ball according to claim10, wherein the outer cover layer comprises at least one materialselected from the group consisting of polyphenylene ether/ionomerblends, ionomers, polyamides, polyurethanes, polyester elastomers,polyester amides, metallocene catalyzed polyolefins, and blends thereof.12. The golf ball according to claim 10, wherein the outer cover layercomprises ionomer.
 13. The golf ball according to claim 10, wherein theouter cover layer comprises polyurethane.
 14. The golf ball according toclaim 10, wherein the golf ball exhibits a spin factor of at least 8.15. A golf ball comprising: an inner ball, the inner ball comprising acore and an inner cover layer disposed about the core, the inner ballhaving a coefficient of restitution of at least 0.780; and an outercover layer disposed about the inner ball, the outer cover layer havinga Shore D hardness of no more than 55 as measured on the curved surfacethereof; wherein the golf ball exhibits a coefficient of restitution ofat least 0.770 and a PGA compression of 100 or less.
 16. The golf ballaccording to claim 15, wherein the inner cover layer of the inner ballcomprises at least one material selected from the group consisting ofpolyphenylene ether/ionomer blends, ionomers, polyamides, polyurethanes,polyester elastomers, polyester amides, metallocene catalyzedpolyolefins, and blends thereof.
 17. The golf ball according to claim15, wherein the inner cover layer of the inner ball exhibits a Shore Dhardness of at least
 60. 18. The golf ball according to claim 15,wherein the outer cover layer comprises at least one material selectedfrom the group consisting of polyphenylene ether/ionomer blends,ionomers, polyamides, polyurethanes, polyester elastomers, polyesteramides, metallocene catalyzed polyolefins, and blends thereof.
 19. Thegolf ball according to claim 18, wherein the outer cover layer comprisesat least one of a thermoset polyurethane, a thermoplastic polyurethane,and combinations thereof.
 20. The golf ball according to claim 19,wherein the outer cover layer comprises a reaction injection moldedpolyurethane.
 21. The golf ball according to claim 18, wherein the outercover layer has a Shore D hardness of from about 30 to about
 55. 22. Agolf ball comprising: a core; an inner cover layer disposed about thecore, the inner cover layer having a Shore D hardness of at least 60 asmeasured on the curved surface thereof and comprising at least onematerial selected from the group consisting of polyphenyleneether/ionomer blends, ionomers, polyamides, polyurethanes, polyesterelastomers, polyester amides, metallocene catalyzed polyolefins, andblends thereof; and an outer cover layer disposed about the inner coverlayer, the outer cover layer having a Shore D hardness of no more than55 as measured on the curved surface thereof and comprising a materialselected from the group consisting of polyphenylene ether/ionomerblends, ionomers, polyamides, polyurethanes, polyester elastomers,polyester amides, metallocene catalyzed polyolefins, and blends thereof;wherein the golf ball exhibits a PGA compression of 100 or less and acoefficient of restitution of at least 0.770.
 23. The golf ballaccording to claim 22, wherein polyurethanes include thermoset andthermoplastic polyurethanes.
 24. The golf ball according to claim 23,wherein the polyurethane is a reaction injection molded polyurethane.25. The golf ball according to claim 22, wherein the outer cover layerhas a Shore D hardness of from about 30 to about
 55. 26. The golf ballaccording to claim 22, wherein the golf ball has a spin factor of atleast 5.0.